Intermodulation distortion reduction in a contact hearing system

ABSTRACT

In embodiments of the invention, the present invention is directed to a contact hearing system including: a transmit circuit including a transmit coil positioned in an ear tip, THE transmit circuit having a first bandpass characteristic, wherein the transmit circuit is tuned such that a center of the first bandpass characteristic is set at a first frequency; and a receive circuit including a receive coil positioned on a contact hearing device, the receive circuit having a second bandpass characteristic, wherein the receive circuit is tuned such that a center of the second bandpass characteristic differs from the center of the first bandpass characteristic.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of PCT Application No.PCT/US19/42935, filed Jul. 23, 2019; which claims the benefit of U.S.Provisional Patent Applications Nos. 62/712,458, filed Jul. 31, 2018;62/712,462, filed Jul. 31, 2018; 62/712,466, filed Jul. 31, 2018;62/712,474, filed Jul. 31, 2018; 62/712,478, filed Jul. 31, 2018;62/831,074, filed Apr. 8, 2019; and 62/831,085, filed Apr. 8, 2019; thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Contact hearing aids (such as, for example, the light based hearing aidavailable from Earlens Corporation) provide significant advantages overair conduction hearing aids, including, for example an expandedbandwidth and a substantial increase in available gain before feedback.However, certain challenges arise when using light as a transmissionmechanism in an environment like the human ear canal. One challenge isthe presence of substances, including cerumen, in the ear canal whichmay partially or fully block light as it is transmitted through the earcanal. For example, in a system that uses a laser positioned in an eartip as a transmission device and a photodetector positioned on a contacthearing device as a detection device, the presence of such substancesmay impede transmission of light at the laser or reception of the lightby the photodetector. A further challenge may be the shape of the earcanal itself, which may impede the transmission of light from alaterally placed laser to a medially placed photodetector since lightwill generally not pass through tissue located between the laser and thephotodetector. This challenge may be even worse in some users where theear canal is highly mobile, the shape changing when the user yawns,chews, coughs or laughs. A further challenge in a light based system isthe need to focus the light from the laser onto the photodetector, whichmay be located on a contact hearing device. This need to focus lightonto the photodetector necessitates alignment between the output of thelaser and the photodetector, which alignment may be effected by themovement of the ear canal described above. One consequence of thesechallenges is the need to place the output of the laser as close aspossible to the photodetector, to ensure that an adequate portion of thelight transmitted from the laser is received at the photodetector. Anfurther challenge it the inherent inefficiency of converting anelectrical signal, such as that generated by an audio processor intolight, such as that generated by a laser and, on the receiving end, theinherent inefficiency of converting a light signal, such as thatreceived by the photodetector, back into an electrical signal. Thisinefficiency means that the system will lose a significant amount ofpower during the light transmission which may result in, for example,reduced battery life.

It would, therefore, be advantageous to design a contact hearing aid inwhich transmission between a laterally located ear tip and a mediallylocated contact hearing device is not degraded by the presence of tissueor other substances between the ear tip and the contact hearing device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of embodimentsof the present inventive concepts will be apparent from the moreparticular description of preferred embodiments, as illustrated in theaccompanying drawings in which like reference characters refer to thesame or like elements. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of thepreferred embodiments.

FIG. 1 is a cutaway view of an ear canal showing a contact hearingsystem according to the present invention wherein at least a portion ofthe contact hearing system is positioned in the ear canal.

FIG. 2 is a block diagram of a contact hearing system according to thepresent invention.

FIG. 3 is a top view of a contact hearing device according to thepresent invention.

FIG. 4 is a bottom view of a contact hearing device according to thepresent invention.

FIG. 5 is a side view of a portion of a contact hearing device,including a drive post and umbo lens, according to the presentinvention.

FIG. 6 is a cutaway view of an ear canal illustrating the positioning ofa contact hearing device according to the present invention.

FIG. 7 illustrates a processor and ear tip according to the presentinvention.

FIG. 8 is a side perspective view of a transmit coil for use in an eartip according to the present invention.

FIG. 9 is an end view of an ear tip according to the present invention.

FIG. 10 is a cut away side view of an ear tip according to the presentinvention.

FIG. 10A is a cut away side view of an ear tip according to the presentinvention.

FIG. 11 is an end view of an ear tip according to the present invention.

FIG. 12 is a cut away side view of an ear tip according to the presentinvention.

FIG. 12A is a cut away side view of an ear tip according to the presentinvention.

FIG. 13A is a top perspective view of a charging station for use incharging processors.

FIG. 13B is a back perspective view of a charging station for use incharging processors.

FIG. 14 is a block diagram of an inductively coupled contact hearingsystem, including a contact hearing device, according to the presentinvention.

FIG. 14A is a block diagram of an inductively coupled contact hearingsystem according to the present invention.

FIG. 15 is a block diagram of a contact hearing system, including an eartip and contact hearing device according to the present invention.

FIG. 16 is a block diagram of a contact hearing system which is adaptedfor communication with external devices according to the presentinvention.

FIG. 17 is a block diagram of a contact hearing device according to thepresent invention.

FIG. 18 is a diagram of a rectifier circuit for use in a contact hearingsystem according to the present invention.

FIG. 18A is a diagram of a rectifier circuit for use in a contacthearing system according to the present invention.

FIG. 19 is a diagram of a rectifier and converter circuit for use in acontact hearing system according to the present invention.

FIG. 20 is a diagram of a rectifier and converter circuit for use in acontact hearing system according to the present invention.

FIG. 21 is a diagram of a portion of a contact hearing device accordingto the present invention.

FIG. 21A is a diagram of a portion of a contact hearing device accordingto the present invention.

FIG. 22 is a circuit diagram of transmitter and receiver components of acontact hearing system according to embodiments of the presentinvention.

FIG. 22A is a circuit diagram of transmitter and receiver components ofa contact hearing system according to embodiments of the presentinvention.

FIG. 23 is a circuit diagram of components of a receiver for use in acontact hearing system according to the present invention.

FIG. 24 is a circuit diagram of components of a receiver for use in acontact hearing system according to the present invention.

FIG. 25 is a circuit diagram of components of a transmitter for use in acontact hearing system according to the present invention.

FIG. 26 is a circuit diagram of components of a transmitter for use in acontact hearing system according to the present invention.

FIG. 27 is a circuit diagram of components of a transmitter for use in acontact hearing system according to the present invention.

FIG. 28 is an illustration of a circuit wherein the DSM input is thedelta-Sigma modulator output signal used to modulate a carrier signal.

FIG. 29 is a system model of a system according to the presentinvention, including transmission and receive tank circuits and adetector circuit.

FIG. 30 illustrates the time domain waveform when the added carrierclock is the same size as the delta sigma signal mixed with the carrierclock.

FIG. 31 illustrates the resulting waveform with a 95% delta sigma withthe added clock.

FIG. 32 is a graph of output in dB SPL as a function of transmit coil toreceive coil distance.

FIGS. 33-35 illustrate various transmit coil vs receive coil alignmentsaccording to the present invention.

FIG. 36 illustrates a receiver according to the present inventionwherein a Villard circuit is used to demodulate the received signal.

FIG. 37 illustrates a receiver according to the present inventionwherein a Greinacher circuit is used to demodulate the received signal.

FIG. 38 is a side view of a transmit coil for use in an ear tipaccording to the present invention.

FIG. 39 is a top view of a transmit coil for use in an ear tip accordingto the present invention.

FIG. 40 is a side perspective view of a transmit coil for use in an eartip according to the present invention.

FIG. 41 is an end view of an ear tip according to the present invention.

FIG. 42 is an end view of an ear tip according to the present invention.

FIG. 43 is a side view of an ear tip assembly according to the presentinvention.

FIG. 44 is a top and side view of a receive coil according to thepresent invention.

FIG. 45 is a perspective view of a receive coil according to the presentinvention.

FIG. 46A is a perspective view of a receive circuit assembly accordingto the present invention.

FIG. 46B is a perspective exploded view of a receive coil according tothe present invention.

FIG. 47 illustrates a receiver according to the present inventionwherein a Greinacher circuit is used to demodulate the received signal.

FIG. 48 illustrates a receiver according to the present inventionwherein a Greinacher circuit is used to demodulate the received signal.

FIG. 49 is an illustration of a circuit wherein the DSM input is thedelta-Sigma modulator output signal used to modulate a carrier signal.

FIG. 50 is an illustration of a circuit wherein the DSM input is thedelta-Sigma modulator output signal used to modulate a carrier signal.

FIG. 51 is a system model of a system according to the presentinvention, including transmission and receive tank circuits and adetector circuit.

FIG. 52 is a graph showing passband tuning according to the presentinvention for a transmit circuit and a receive circuit according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cutaway view of an ear canal showing a contact hearingsystem 110 for use in systems and methods according to the presentinvention, wherein at least a portion of the contact hearing system 110is positioned in the ear canal. In embodiments of the invention, contacthearing system 110 may be referred to as a smartlens system orsmartlens. In embodiments of the invention, contact hearing system 110may comprise a contact hearing system using electromagnetic waves totransmit information and/or power from ear tip 120 to the contacthearing device 112. In embodiments of the invention, contact hearingsystem 110 may comprise a contact hearing system using inductivecoupling to transmit information and/or power from ear tip 120 tocontact hearing device 112. In FIG. 1, contact hearing system 110includes Audio processor 132, which audio processor may include at leastone external microphone 310. Audio processor 132 may be connected to anear tip 120 by cable 260, which is adapted to transmit signals fromaudio processor 132 to ear tip 120. Ear tip 120 may further includecanal microphone 312 and at least one acoustic vent 338. Ear tip 120 maybe an ear tip which radiates electromagnetic waves 142 in response tosignals from audio processor 132. Electromagnetic signals radiated byear tip 120 may be received by contact hearing device 112, which maycomprise receive coil 130, microactuator 140, and umbo platform 220. Asused herein, receive coil 130 may comprise receive circuit assembly 1084as illustrated in FIGS. 44-46.

FIG. 2 is a block diagram of a contact hearing system 110 for use inmethods and apparatus according to the present invention. In embodimentsof the invention, at least a portion of contact hearing system 110 ispositioned in the ear canal of a user. In FIG. 2, ambient sound 340 maybe received by external microphone 310 of audio processor 132, whichthen processes the received sound by passing it through processingcircuitry, which may include analog to digital converter 320 and digitalsignal processor 330. The output of audio processor 132 may betransmitted to an ear tip 120 by cable 260. Signals transmitted to eartip 120 may then be transmitted to contact hearing device 112 by, forexample, causing transmit coil 290 to radiate electromagnetic waves 142.In embodiments of the invention, contact hearing device 112 may includereceive coil 130, microactuator 140, and umbo lens 220. Informationcontained in electromagnetic waves 142 received by receive coil 130 maybe transmitted through demodulator 116 to microactuator 140, moving umbolens 220. In embodiments of the invention, the signal transmitted to eartip 120 may be a signal representative of the received audio signalwhich may then be transmitted to contact hearing device 112. Inembodiments of the invention, transmit coil 290 may be wound around anacoustic vent 338 in ear tip 120. In embodiments of the invention,acoustic vent 338 may be formed as a passage through a ferrite materialor a ferromagnetic material. As used herein ferrite material may be anyferromagnetic material. In embodiments of the invention, transmit coil290 may be wound around ferrite material positioned in ear tip 120. Inembodiments of the invention, contact hearing system 110 may include oneor more external communication and control devices 324, such as, forexample, a cell phone. In embodiments of the invention, audio processor132 may communicate with external communication and control devices 324by, for example, using audio processor antenna 134.

FIG. 3 is a top view of a contact hearing device 112 according to thepresent invention. FIG. 4 is a bottom view of a contact hearing device112 according to the present invention. The contact hearing device 112illustrated in FIGS. 3 and 4 includes a receive coil 130, amicroactuator 140, an umbo lens 220, a support structure 141, andsprings 144. In the embodiment illustrated in FIGS. 3 and 4,microactuator 140 is connected to support structure 141 by springs 144.In embodiments of the invention, contact hearing device 112 may furtherinclude a sulcus platform 118, which may also be referred to as amounting platform, connected to support structure 141 and adapted toassist in positioning contact hearing device 112 in the ear canal of auser. In embodiments of the invention, contact hearing device 112 mayfurther include grasping tab 114.

FIG. 5 is a side view of a portion of a contact hearing device 112according to the present invention, including a drive post 124 and umbolens 220. In FIG. 5, contact hearing device 112, including a drive post124 and umbo lens 220. In FIG. 5, drive post 124 may be attached to umbolens 220 by adhesive 122. Drive post 124 may be attached to the outputof microactuator 140, which is supported on contact hearing device 112by support structure 141.

FIG. 6 is a cutaway view of an ear canal illustrating the positioning ofa contact hearing device 112 according to the present invention. In theembodiment of FIG. 6, contact hearing device 112 is positioned at amedial end of the ear canal, proximate the tympanic membrane of theuser. Contact hearing device 112 includes a receive coil 130 positionedat a medial end thereof. In embodiments of the invention, receive coil130 may be positioned to receive signals from an ear tip (not shown)positioned in the ear canal lateral to the position of contact hearingdevice 112. In embodiments of the invention, signals received by receivecoil 130 may be transmitted to microactuator 140 to move drive post 124which is connected to the user's tympanic membrane through umbo lens220. Umbo lens 220 may be in direct physical contact with the tympanicmembrane or a thin layer of oil 126 may be used between umbo lens 220and the user's tympanic membrane. Sulcus platform 118 may be used toproperly position contact hearing device 112 in the user's ear canalthrough contact with a skin layer which lines the ear canal. Sulcusplatform 118 may be in direct contact with the skin of the ear canal ora thin layer of oil 126 may be used between sulcus platform 118 and theskin of the ear canal. In embodiments of the invention contact hearingdevice 112 may further include support structure 141, grasping tab 114,and springs 144.

FIG. 7 illustrates an audio processor 132 and ear tip 120 according tothe present invention. Ear tip 120 may, in some embodiments of theinvention, be referred to as a mag tip or magnetic tip. In theembodiment of FIG. 7, audio processor 132 may include externalmicrophones 310 and volume/control switch 314. In embodiments of theinvention, ear tip 120 may include a transmit coil 290 which may includeferrite core 318. In embodiments of the invention, ear tip 120 mayinclude an acoustic vent which may pass through transmit coil 290 and/orthrough ferrite core 318

FIG. 8 is a side perspective view of a transmit coil 290 for use in anear tip 120 according to the present invention. In the embodiment ofFIG. 8, transmit coil 290 includes coil winding 316 which is woundaround ferrite core 318. In embodiments of the invention, transmit coil290 may further include acoustic vent 338. In embodiments of theinvention, transmit coil 290 may further include transmit electronics342. In embodiments of the invention, transmit coil 290 may be connectedto audio processor 132 by cable 260.

FIG. 9 is an end view of an ear tip 120 according to the presentinvention. FIGS. 10 and 10A are cut away side views of an ear tipaccording to the present invention. FIG. 11 is an end view of an ear tip120 according to the present invention. FIGS. 12 and 12A are cut awayside views of an ear tip 120 according to the present invention. In theembodiments of FIGS. 9, 10, 10A, 11, 12, and 12A, ear tip 120 includesmounting recess 334, which is adapted to receive transmit coil 290(shown in FIGS. 10A and 12A). In the embodiments of FIGS. 9-12, ear tip120 further includes at least one secondary acoustic vent 336. Inembodiments of the invention, secondary acoustic vents are adapted towork in conjunction with acoustic vent 338 in transmit coil 290 toreduce the overall acoustic mass of the ear tip. In embodiments of theinvention, secondary acoustic vents 336 combine at central chamber 332which has a larger cross section than the combined cross section ofsecondary acoustic vents 336. In embodiments of the invention, secondaryacoustic vents 336 and acoustic vent 338 combine at central chamber 332which has a larger cross section than the combined cross section ofsecondary acoustic vents 336 and acoustic vent 338.

In embodiments of the invention, the total combined acoustic mass(including the acoustic mass of acoustic vent 338 through ferrite core318 of transmit coil 290, the acoustic mass of any secondary acousticvents 336 and the acoustic mass of central chamber 332) will not exceed2000 Kg/m⁴. In embodiments of the invention, the acoustic mass may bedefined as the impeding effect of inertia upon the transmission of soundin a conduit, equal in a tubular conduit (as an organ pipe) to the massof the vibrating medium divided by the square of the cross section. Itmay also be the acoustic analogue of alternating-current-circuitinductance (called also inertance). In an ear tip which incorporates oneor more acoustic vents, the acoustic mass may be representative of theresistance to the flow of air through the ear tip. The acousticimpedance (Z) is frequency specific and relates to the acoustic mass (orinertance, L) as a function of frequency Z=jwL. Acoustic mass may be afunction of the cross section of any acoustic vents in an ear tip.Acoustic mass may be a function of the effective length of the acousticvents in an ear tip. A higher acoustic mass may be perceived by thehearing aid user in a fashion similar to what would be perceived whentalking with one's fingers in the ear canals. Thus, a higher acousticmass effect may be perceived to result in altering the hearing aiduser's voice in ways which the hearing aid user finds to be bothersomeor unacceptable.

For an even straight tube, the acoustic mass is Oven by the simpleequation:

$\frac{\rho l}{A}$

Where ρ is the density of air (in kg/m3), l is the length of the tube,and A is the cross sectional area along the open bore.

For complex openings, the acoustic mass can be described as the integralof the density of air (ρ) divided by the open cross sectional area alongthe length of the light tip:

$\int\limits_{ϰ = 0}^{{tip}\mspace{11mu} {length}}{\frac{\rho}{Area_{ϰ}}dx}$

Which can be estimated by dividing the tip along its length into n crosssections and summing each open area as follows:

$\sum\limits_{i = 0}^{n}{\frac{\rho}{Area_{i}}x\Delta l}$

Where:

${\Delta l} = \frac{{tip}\mspace{14mu} {length}}{n}$

In one embodiment, the present invention is directed to an ear tiphaving a proximal end and a distal end, the eartip including: a transmitcoil, the transmit coil including a core of a ferromagnetic material,the ferromagnetic core having a central channel there through, a distalend of the ferromagnetic core positioned at a first opening in a distalend of the ear tip; a passage extending from an opening at a proximalend of the ear tip to the distal end of the ear tip, the passage endingat a second opening in the distal end of the ear tip, wherein a proximalend of the central channel is connected to the passage. In embodimentsof the present invention, the combination of the central channel and thepassage act as an acoustic vent, allowing air and sound to pass throughthe ear tip. In embodiments of the present invention, the acoustic venthas a predetermined acoustic mass. In embodiments of the presentinvention, the predetermined acoustic mass of the ear tip is less than2000 kilograms per meter⁴ (meter to the fourth power). In embodiments ofthe present invention, the transmit coil includes a coil winding woundaround the ferromagnetic material.

In one embodiment, the present invention is directed to a method ofacoustically connecting a proximal end of an ear tip to a distal end ofan ear tip wherein the ear tip includes a transmit coil wrapped around acore, the core having an central channel extending from a proximal endof the core to a distal end of the core, and the ear tip having apassage extending from a proximal end of the ear tip to a distal end ofthe ear tip, the method including the steps of: passing an electricalcurrent through the transmit coil; passing acoustic signals through thecentral channel; and passing acoustic signals through the passage. Inembodiments of the present invention, the acoustic signals comprisesound. In embodiments of the present invention, sound and air passthrough the passage. In embodiments of the present invention, a proximalend of the central channel connects to the passage at a point within theear tip. In embodiments of the present invention, a distal end of thecentral channel is connected to a first opening in the distal end of theear tip and the distal end of the passage is connected to a secondopening in the distal end of the ear tip.

FIG. 13A is a top perspective view of a charging station 136 for use incharging audio processors 132. FIG. 13B is a back perspective view of acharging station 136, including AC adapter port 134 for use in chargingaudio processors 132. In FIGS. 13A and 13B, audio processors 132 may bepositioned in charging slots 138. Charging status LEDs 128 may be usedto communicate the charge status of audio processors 132 positioned incharging slots 138.

FIG. 14 is a block diagram of an inductively coupled contact hearingdevice 112 and ear tip 120 according to the present invention. Inembodiments of the invention, contact hearing device 112 may also bereferred to as a medial ear canal assembly. In FIG. 14, the output ofear tip 120 may be inductively coupled through transmit coil 290 toreceive coil 130 on contact hearing device 112. In embodiments of theinvention, ear tip 120 may be referred to as a lateral ear canalassembly. In embodiments of the invention, inductive coupling may inducea current in receive coil 130 on contact hearing device 112. Inembodiments of the invention, the inductively induced current may bemeasured by current sensor 852. In embodiments of the invention,inductive coupling may induce an output voltage V₁ across receive coil130. In embodiments of the invention, the induced output voltage may bemeasured by a voltage meter 863. In embodiments of the invention, themeasured current and voltage may be used by MPPT control 848 and dataacquisition circuit 846. In embodiments of the invention, the output ofreceive coil 130 may be further connected to a rectifier and convertercircuit 865 through capacitor 854. In embodiments of the invention,receive coil 130 may be connected directly to rectifier and convertercircuit 865 (eliminating capacitor 854). In embodiments of theinvention, receive coil 130 may be connected to a rectifier circuit. InFIG. 14, capacitor 854 may be positioned between the output of receivecoil 130, which may include capacitor 872, and the input of rectifierand converter circuit 865. The output of rectifier and converter circuit865 may be connected to load 882 and to storage device 869. Inembodiments of the invention, rectifier and converter circuitry 865 mayinclude circuitry which provides power to storage device 869 andtransmits power from storage device 869 to load 882 when required. Inembodiments of the invention, storage device 869 may be connecteddirectly to receive coil 130 or to other circuitry adapted to harvestenergy from receive coil 130 and deliver energy to load 882. Load 882may be, for example, a microactuator positioned on the contact hearingdevice 112 such that load 882 vibrates the tympanic membrane of a userwhen stimulated by signals received by receive coil 130. Storage device869 may be, for example, a rechargeable battery.

In embodiments of the invention, transmit coil 290 may comprise atransmit coil, such as, for example, transmit coil 290 and coil 130 maycomprise a receive coil, such as, for example, receive coil 130. Inembodiments of the invention, transmit coil 290 and receive coil 130 maybe elongated coils manufactured from a conductive material. Inembodiments of the invention, transmit coil 290 and receive coil 130 maybe stacked coils. In embodiments of the invention, transmit coil 290 andreceive coil 130 may be wound inductors. In embodiments of theinvention, transmit coil 290 and receive coil 130 may be wound around acentral core. In embodiments of the invention, transmit coil 290 andreceive coil 130 may be wound around a core comprising air. Inembodiments of the invention, transmit coil 290 and receive coil 130 maybe wound around a magnetic core. In embodiments of the invention,transmit coil 290 and receive coil 130 may have a substantially fixeddiameter along the length of the wound coil.

In embodiments of the invention, rectifier and converter circuit 865 maycomprise power control circuitry. In embodiments of the invention,rectifier and converter circuit 865 may comprise a rectifier. Inembodiments of the invention, rectifier and converter 865 may be arectifying circuit, including, for example, a diode circuit, a half waverectifier or a full wave rectifier. In embodiments of the invention,rectifier and converter circuit 865 may comprise a diode circuit andcapacitor. In embodiments of the invention, energy storage device 869may be a capacitor, a rechargeable battery or any other electronicelement or device which is adapted to store electrical energy.

In FIG. 14, the output of MPPT control circuit 848 may control rectifierand converter circuit 865. Rectifier and converter circuit 865 maysupply energy to and receive energy from storage device 869, which maybe, for example, a rechargeable battery. Data acquisition circuit 846and rectifier and converter circuit 865 may be used to drive load 882,with data acquisition circuit 846 proving load 882 with control data(e.g. sound wave information) and rectifier and converter circuit 865providing load 882 with power. In embodiments of the invention,rectifier and converter circuit 865 may be used to drive load 882directly, without information from a data circuit such as dataacquisition circuit 846. In embodiments of the invention, rectifier andconverter circuit 865 may be used to drive load 882 directly withoutenergy from storage device 869. The power provided by rectifier andconverter circuit 865 may be used to drive load 882 in accordance withthe control data from data acquisition circuit 846. Load 882 may, insome embodiments of the invention, be a transducer assembly, such as,for example, a balanced armature transducer.

In embodiments of the invention, information and/or power may betransmitted from ear tip 120 to contact hearing device 112 bymagnetically coupling transmit coil 290 to receive coil 130. When thecoils are inductively coupled, the magnetic flux generated by transmitcoil 290 may be used to generate an electrical current in receive coil130. When the coils are inductively coupled, the magnetic flux generatedby transmit coil 290 may be used to generate an electrical voltageacross receive coil 130. In embodiments of the invention, the signalused to excite transmit coil 290 on ear tip 120 may be a push/pullsignal. In embodiments of the invention, the signal used to excitetransmit coil 290 may have a zero crossing. In embodiments of theinvention, the magnetic flux generated by transmit coil 290 travelsthrough a pathway that includes a direct air pathway that is notobstructed by bodily components. In embodiments of the invention, thedirect air pathway is through air in the ear canal of a user. Inembodiments of the invention, the direct air pathway is line of sightbetween ear tip 120 and contact hearing device 112 such that contacthearing device 112 is optically visible from ear tip 120.

In embodiments of the invention, the output signal generated at receivecoil 130 may be rectified by, for example, rectifier and convertercircuit 865. In embodiments of the invention, a rectified signal may beused to drive a load, such as load 882 positioned on contact hearingdevice 112. In embodiments of the invention, the output signal generatedat receive coil 130 may contain an information/data portion whichincludes information transmitted to contact hearing device 112 bytransmit coil 290. In embodiments of the invention, at least a portionof the output signal generated at receive coil 130 may contain energy orpower which may be scavenged by circuits on contact hearing device 112to charge, for example, storage device 869.

FIG. 14A is a block diagram of an inductively coupled contact hearingsystem according to the present invention. In FIG. 14A, contact hearingsystem 110 includes Ear Tip 120 (which may also be referred to as a MagTip) and contact hearing device 112. Ear Tip 120 may include a transmitcoil 290. Contact hearing device 112 may include receive coil 130,parasitic capacitance 872, capacitor 854, rectifier and convertercircuit 865 and load 882.

FIG. 15 is a block diagram of a contact hearing system 110, including aear tip 120 (which may also be referred to as a processor) and contacthearing device 112 according to the present invention. In FIG. 15, eartip 120 may include an external antenna 802 adapted to send and receivesignals from an external source such as a cell phone (see FIG. 2).External antenna 802 may be connected to a circuit for processingsignals received from external antenna 802, such as blue tooth circuit804, which, in some embodiments, may be a blue tooth low energy circuit.The output of Bluetooth circuit 804 may be connected to digital signalprocessor 840, which may also include inputs from microphones 810. Earcanal assembly 12 may further include battery 806 and power conversioncircuit 808 along with charging antenna 812 (which may be a coil) andwireless charging circuit 814. Digital signal processor 840 may beconnected to interface circuit 816, which may be used to transmit dataand power from ear tip 120 to contact hearing device 112. In embodimentsof the invention, power and data may be transmitted between ear tip 120and contact hearing device 112 over power/data link 818 by inductivecoupling to provide transmission of the data and power. Alternatively,separate modes of transmission may be used for the power and datasignals, such as, for example, transmitting the power using radiofrequency or light and the data using inductive coupling.

In FIG. 15, power and data transmitted to contact hearing device 112 maybe received by interface circuit 822. Interface circuit 822 may beconnected to energy harvesting and data recovery circuit 824 and toelectrical and biological sensors 823. In FIG. 2, contact hearing device112 may further include energy storage circuitry 826, power managementcircuitry 828, data and signal processing circuitry 832, andmicrocontroller 834. Contact hearing device 112 may further include adriver circuit 836 and a microactuator 838. In the illustratedembodiment, data transmitted from contact hearing device 112 may bereceived by interface circuit 816 on ear tip 120.

FIG. 16 is a block diagram of a contact hearing system 110, adapted forcommunication with external devices according to the present invention.In FIG. 3, contact hearing system 110 is adapted to communicate withexternal devices such as cell phone 844 or cloud computing services 842.Such communication may occur through, for example, external antenna 802on ear tip 120 or, in some embodiments directly from contact hearingdevice 112.

FIG. 17 is a block diagram of a contact hearing device 112 according toan embodiment of the present invention. In FIG. 17, contact hearingdevice 112 includes interface 720, clock recovery circuit 730, datarecovery circuit 740 and energy harvesting circuit 750. In embodimentsof the invention, interface 720 is adapted to transmit data from contacthearing device 112 and to receive data transmitted to contact hearingdevice 112. Interface 720 may be an inductive interface. Contact hearingdevice 112 may further include power management circuit 760, voltageregulator 770, driver 780, data processor encoder 790 and data/sensorinterface 800.

In FIG. 17, upstream data 702 collected from data processor/encoder 790may be transmitted via interface 720 as a part of upstream signal 700.Downstream signal 710 may be transmitted to interface 720, which mayextract the data portion and may distribute downstream data 712 to datarecovery circuit 740 and clock recovery circuit 730. Interface 720 mayfurther transmit at least a portion of downstream signal 710 to energyharvesting circuit 750. The output of energy harvesting circuit 750 maybe transmitted to power management circuit 760, which may thendistribute energy to voltage regulator 770. Voltage regulator 770 maydistribute its output to driver 780, which may also receive input fromdata recovery circuit 740. The output of driver 780 may be sent throughmatching network 831 to drive, for example, microactuator 840.

Microactuator 840 may include sensors (not shown) which generate dataabout the function of microactuator 840. This data may be transmittedback to contact hearing device 112 through matching network 831 and todata/sensor interface 800, which, in turn may transmit the sensorinformation to data processor/encoder 790, which generates upstream data702. Data/sensor interface 800 may also receive information from othersensors (e.g. Sensor 1 to Sensor n in FIG. 4), which data is, in turn,transmitted to data processor/encoder 790 and becomes part of upstreamdata 702.

FIG. 18 is a diagram of a rectifier and converter circuit 865 accordingto the present invention. In FIG. 18, rectifier and converter circuit865 may include diode 974 and capacitor 972. In embodiments of theinvention, the input to rectifier and converter circuit 865 may beconnected directly to receive coil 130. In embodiments of the invention,the output of rectifier and converter circuit 865 may be coupleddirectly to a load, such as, for example, a transducer or a balancedarmature transducer. In embodiments of the invention, the output ofrectifier and converter circuit 865 may be coupled to the windings in aload, such as, for example, a transducer or a balanced armaturetransducer.

FIG. 18A is a diagram of a rectifier and converter circuit 865 accordingto the present invention. In embodiments of the invention, rectifier andconverter circuit 865 may comprise a Villard Circuit. In embodiments ofthe invention, rectifier and converter circuit 865 may be a voltagemultiplier circuit. In FIG. 18, rectifier and converter circuit 865 mayinclude diode 974, AC filter capacitor 975 (which may be a seriescapacitor) and resonant capacitor 977. In embodiments of the invention,the input to rectifier and converter circuit 865 may be connecteddirectly to receive coil 130. In embodiments of the invention, theoutput of rectifier and converter circuit 865 may be coupled directly toa load, such as, for example, a transducer or a balanced armaturetransducer. In embodiments of the invention, the output of rectifier andconverter circuit 865 may be coupled to the windings in a load, such as,for example, a transducer or a balanced armature transducer.

FIG. 19 is a diagram of an alternative rectifier and converter circuit865 according to the present invention. In embodiments of the invention,rectifier and converter circuit 865 may include diodes 974 andcapacitors 972 which may form, for example bridge circuits such as, forexample a half wave bridge.

FIG. 20 is a diagram of an alternative rectifier and converter circuitaccording to the present invention. In embodiments of the invention,rectifier and converter circuit 865 may include diodes 974 andcapacitors 972 which may form, for example bridge circuits such as, forexample, a full wave bridges. In embodiments of the invention, rectifierand converter circuit 865 may be connected to receive coil 130.

FIG. 21 is a diagram of a portion of a contact hearing device 112according to the present invention. In embodiments of the invention, theinput to rectifier and converter circuit 865 may be connected to receivecoil 130 through additional circuitry, such as, for example, capacitor854 or input circuitry 976. In embodiments of the invention, the outputof rectifier and converter circuit 865 may be coupled to a load, suchas, for example, a transducer or a balanced armature transducer throughan output circuit 978. In embodiments of the invention, output circuit978 may be, for example, a capacitor, an inductor, a combination ofelectrical or electronic components and/or a matching circuit.

FIG. 21A is a diagram of a portion of a contact hearing device accordingto the present invention. In FIG. 21A, contact hearing device 112 mayinclude receive coil 130, connected to rectifier and converter circuit865, which, in turn, may be connected to load 882, which may be, forexample, a microactuator, for example a balanced armature microactuator.

FIG. 22 is a circuit diagram of transmitter and receiver components of acontact hearing system 110 according to embodiments of the presentinvention. In embodiments of the invention, ear tip 120 may include adrive circuit 988, which may also be referred to as a transmit circuit.Drive circuit 988 may include coil L1 980 and signal source 996. Inembodiments of the invention, ear tip 120 may further include transmitresonant circuit 992. In embodiments of the invention, transmit resonantcircuit 992 may include resonant transmit coil L2 994 and resonanttransmit capacitor C1 998. In embodiments of the invention, contacthearing device 112 may include load circuit 990. In embodiments of theinvention, load circuit 990 may include load coil 982, voltage detector1002, rectifier 1004 and load 1006. In embodiments of the invention,contact hearing device 112 may include receive resonant circuit 994. Inembodiments of the invention, receive resonant circuit 994 may includeresonant receive coil 986 and resonant receive capacitor C2 1000.

FIG. 22A is a circuit diagram of transmitter and receiver components ofa contact hearing system according to embodiments of the presentinvention. In the contact hearing system 110 of FIG. 22A, ear tip 120includes drive coil L1 980. In the contact hearing system 110 of FIG.22A, contact hearing device 112 includes load coil L4 982, resonancecapacitor 977 (which may also be referred to as a tuning capacitor), ACfilter capacitor 975, rectifier circuit 1004 and load 1006.

In embodiments of the invention, drive coil 980 may be a transmit coilsuch as, for example, transmit coil 290. In embodiments of theinvention, load coil 982 may be a receive coil such as, for example,receive coil 130. In embodiments of the invention, rectifier 1004 may bea rectifier and converter circuit such as, for example, rectifier andconverter circuit 865. In embodiments of the invention, load 1006 may bean actuator, such as, for example microactuator 140. In embodiments ofthe invention, microactuator 140 may be, for example, a balancedarmature microactuator.

FIGS. 23 and 24 are circuit diagrams of components of a receiver 1016for use in a contact hearing system 110 according to the presentinvention. In embodiments of the invention, receiver 1016 may beconstructed in a full-wave rectifier receiver configuration, including asmoothing capacitor. In embodiments of the invention, receiver 102includes receive inductor Lrx 1008, receive capacitor array 1030, diodebridge 1032, motor 1028, and smoothing capacitor 1026. In embodiments ofthe invention, receive capacitor array 1030 may include one or morereceive capacitors, such as, receive capacitor Cr1 1010, receivecapacitor Cr2 1012 and receive capacitor Cr3 1014. In embodiments of theinvention, diode bridge 1034 may include one or more diodes, such as,diode D1 1018, diode D2 1020, diode D3 1022, and diode D4 1024. Inembodiments of the invention, diode bridge 1034 may be arranged as afull wave rectifier bridge with a load, such as, for example, motor 1028connected across the output of the full wave rectifier. In embodimentsof the invention (such as the one illustrated in FIG. 23), a smoothingcapacitor Cs 1026 may be connected across the output of the full waverectifier in parallel with the motor 1028. In embodiments of theinvention (such as the one illustrated in FIG. 24), the smoothingcapacitor may be omitted. In embodiments of the invention, the diodesused in diode bridge 1034 may be Schottky diodes. In embodiments of theinvention, the electrical characteristics of motor 1028 may berepresented by the series circuit which includes motor resistor 1030,representing the resistance of the circuitry in motor 1028 and motorinductor 1032, representing the inductance of motor 1028 at thefrequency of operation.

FIG. 25 is a circuit diagram of components of a transmitter 1036 for usein a contact hearing system 110 according to the present invention. Inembodiments of the invention, transmitter 1036 may be a current source1038 connected in parallel with one or more output capacitors, such asC0 1040 and output coil L1 1042. In the embodiment of the invention,illustrated in FIG. 25, the transmitter may be a parallel drive with thesignal input modeled as current source 1038. The configurationillustrated in FIG. 25 is advantageous because it requires a low inputcurrent.

FIG. 26 is a circuit diagram of components of a transmitter 1036 for usein a contact hearing system 110 according to the present invention. Inembodiments of the invention, transmitter 1036 may be modeled as avoltage source 1044 feeding a capacitive transformer/divider 1046through a resistor R1 1048. In this embodiment, capacitivetransformer/divider 1046 may be modeled as Capacitor C01 1050 in serieswith capacitor C02 1052, which are in parallel with inductor L1 1054.The embodiment of the transmitter, illustrated in FIG. 26 isadvantageous because it may be used to generate a large VL1 when V1 issmall, thus allowing the circuit to be driven by, for example, a batteryhaving a limited output voltage, for example, an output voltage in therange of 3 Volts. In this embodiment, voltage source V1 1044, inparallel with resistor R1 1048, combine to form a quasi-current source.In the embodiment illustrated, the resonant frequency will be a functionof the series combination of capacitor C01 1050, capacitor C02 1052 andInductor L1 1054.

FIG. 27 is a circuit diagram of components of a transmitter 1036 for usein a contact hearing system 110 according to the present invention. Inembodiments of the invention, the circuit illustrated may represent aparallel drive arrangement for transmitter 1036. In embodiments of theinvention, transmitter 1036 may be modeled as a voltage source V1 1044feeding a parallel drive circuit 1056. In embodiments of the invention,parallel drive circuit 1056 may include capacitor C7 1058, capacitor C11060 and inductor L1 1054. In embodiments of the invention, capacitor C71058 adds impedance to voltage source V1 1044 to create a quasi-currentsource. In embodiments of the invention, C7 may be small compared to C11060 in order to ensure that most of the tank current flows in the L1-C1loop, rather than in the L1-C7 loop. In embodiments of the invention,the resonant frequency will depend on the series combination of inductorL1 1054 with the parallel combination of capacitor C1 1060 and capacitorC7 1058.

In embodiments of the invention, using inductive coupling for powerand/or data transfer in a contact hearing system may result in benefitsover other methods of power and/or data transfer, including: reducedsensitivity to directionality; reduced sensitivity to motion incomponents of the contact hearing system; improved patient comfort;reduced sensitivity to the presence of bodily fluids, including cerumen;reduced sensitivity to the presence of tissue between the ear tip andthe contact hearing device; reduced sensitivity to tissue loading;reduced sensitivity to the distance between the ear tip and the contacthearing device. In embodiments of the invention, power and data transfermay be separated (e.g. different frequencies) or combined.

In embodiments of the invention, data and power may be transferred froman ear tip to a contact hearing device using near field magneticcoupling. In embodiments of the invention, data may be transferred froman ear tip to a contact hearing device using near field magneticcoupling. In embodiments of the invention, power may be transferred froman ear tip to a contact hearing device using near field magneticcoupling. In embodiments of the invention, the use of near fieldmagnetic coupling results in a power transfer wherein the power outputfrom the contact hearing device remains relatively constant even whenthe distance between the ear tip and the contact hearing device varies.In embodiments of the invention, as illustrated in FIG. 32, the use ofnear field magnetic coupling results in a power output wherein theoutput of the contact hearing device varies by less than 2 dB SPL whenthe distance between the ear tip and the contact hearing device variesbetween 3 and 7 millimeters. In embodiments of the invention, asillustrated in FIG. 32, the use of near field magnetic coupling resultsin a power output wherein the output of the contact hearing devicevaries by less than 2 dB SPL when the distance between the ear tip andthe contact hearing device is approximately 3 millimeters. Inembodiments of the invention, data and power may be transmitted from anear tip to a contact hearing device using resonant inductive coupling.In embodiments of the invention, the receive coil and the transmit coilmay be connected through resonant inductive coupling. In embodiments ofthe invention, data and power may be transmitted from an ear tip to acontact hearing device using near field magnetic induction. Inembodiments of the invention, data and power may be transmitted from anear tip to a contact hearing device using a near field magneticinduction link.

In embodiments of the invention, such near field magnetic coupling couldalso be used to remotely power and/or deliver signal to neuro-stimimplants. In embodiments of the invention, the actuator may be replacedby electrodes. In embodiments of the invention, such near field magneticcoupling could also be used to remotely power in-body valves for, forexample, bladder control.

In embodiments of the invention, the separation between the transmitcoil and the receive coil may be between approximately five and ninemillimeters when the system is placed in a user's ear.

In one embodiment, the present invention is directed to a method oftransmitting information from an ear tip to a contact hearing device,the method including the steps of: exciting a transmit coil, thetransmit coil being positioned in the ear tip, wherein the transmit coilis wound on a core, the core including a ferromagnetic material;radiating an electromagnetic field from the first coil through the earcanal of a user; receiving the radiated electromagnetic field at areceive coil, the receive coil being positioned on a contact hearingdevice, the contact hearing device including a receive coil without aferrite core; and transmitting the information from the transmit coil tothe receive coil using near-field radiation. In embodiments of theinvention, the ear tip includes the transmit coil and the contacthearing device includes the receive coil. In embodiments of theinvention, the method includes the step of adapting the ear tip suchthat it positions the medial end of the transmit coil to be withinbetween 3 and 7 millimeters of the lateral end of the receive coil whenthe ear tip and contact hearing device are positioned in the ear canalof a user. In embodiments of the invention, the method includes the stepof adapting the ear tip such that when it is positioned in the ear canalof a user more than fifty percent of magnetic flux lines emanating fromthe transmit coil couple through the receive coil. In embodiments of theinvention, the method includes the step of adapting the ear tip suchthat when it is positioned in the ear canal of a user more than seventyfive percent of a magnetic field generated by the transmit coil iscoupled to the receive coil. In embodiments of the invention, the methodincludes the step of generating a signal in the transmit coil inducescurrent in the receive coil, wherein the induce current is induced bythe presence of a magnetic field generated at the transmit coil. Inembodiments of the invention, the current induced is proportional to themagnetic field at the transmit coil. In embodiments of the invention,the step of generating a signal in the transmit coil results in avoltage generated across the receive coil wherein the generated voltageis a product of the magnetic field generated at the transmit coil. Inembodiments of the invention, the voltage generated is proportional tothe magnetic field at the transmit coil. In embodiments of theinvention, the transmitted information is transmitted in an amplitudemodulated (AM) signal. In embodiments of the invention, the transmittedinformation is demodulated by a demodulator attached to a receive coil.In embodiments of the invention, the transmit coil is magneticallycoupled to the receive coil. In embodiments of the invention, thecoupling between the transmit and receive coils is between approximately0.1 percent and approximately 3.0 percent. In embodiments of theinvention, information and power are transmitted from the transmit coilto the receive coil through the interaction of magnetic fields generatedin the transmit coil with the receive coil. In embodiments of theinvention, the core includes a ferrite material.

In one embodiment, the present invention is directed to a method oftransmitting information from an ear tip to a contact hearing device,the method including the steps of: exciting a transmit coil, thetransmit coil being positioned in an ear tip, wherein the transmit coilis wound on a ferrite core; radiating an electromagnetic field from thefirst coil through the ear canal of a user; receiving the radiatedelectromagnetic field at a receive coil, the receive coil beingpositioned on a contact hearing device without a ferrite core; andtransmitting the information from the transmit coil to the receive coilusing a near-field radiation. In embodiments of the invention, the firstand second coils are inductively coupled. In embodiments of theinvention, inductive coupling is used to link the first coil to thesecond coil. In embodiments of the invention, the information istransmitted from the first coil to the second coil using near-fieldmagnetic coupling. In embodiments of the invention, the information istransmitted from the first coil to the second coil using resonantinductive coupling. In embodiments of the invention, the information istransmitted from the first coil to the second coil using near-fieldmagnetic induction. In embodiments of the invention, the information istransmitted from the first coil to the second coil using a near-fieldmagnetic induction link. In embodiments of the invention, the output ofthe contact hearing device varies by less than two decibels soundpressure level (dB SPL) when the distance between the transmit andreceive coils varies by between three and seven millimeters. Inembodiments of the invention, the receive coil is a part of a receivecoil assembly, the receive coil assembly including: the receive coil; atleast one disk positioned at a distal end of the receive coil, the atleast one disk including a ferromagnetic material. In embodiments of theinvention, the receive coil is wound with a central core of anon-ferromagnetic material. In embodiments of the invention, thenon-ferromagnetic material is, at least in part, air. In embodiments ofthe invention, the outer diameter of the at least one disk issubstantially the same as the outer diameter of the receive coil. Inembodiments of the invention, the at least one disk includes a holetherethrough. In embodiments of the invention, the at least one disk istwo disks. In embodiments of the invention, a printed circuit boardincluding electronic components is affixed to a side of the at least onedisk opposite the side to which the receive coil is affixed. Inembodiments of the invention, the at least one disk includes a ferritematerial.

In one embodiment, the present invention is directed to a method oftransmitting information from an ear tip to a contact hearing device,the method including the steps of: exciting a transmit coil, thetransmit coil being positioned in an ear tip, wherein the transmit coilis wound on a ferromagnetic core; radiating an electromagnetic fieldfrom the transmit coil through an ear canal of a user; receiving theradiated electromagnetic field at a receive coil, the receive coil beingpositioned on a contact hearing device, the receive coil having a coreof a non-ferromagnetic material; and transmitting the information fromthe transmit coil to the receive coil using the electromagnetic field.In embodiments of the invention, the transmit and receive coils areinductively coupled. In embodiments of the invention, inductive couplingis used to link the transmit coil to the receive coil. In embodiments ofthe invention, the information is transmitted from the transmit coil tothe receive coil using near-field magnetic coupling. In embodiments ofthe invention, the information is transmitted from the transmit coil tothe receive coil using resonant inductive coupling. In embodiments ofthe invention, information is transmitted from the transmit coil to thereceive coil using near-field magnetic induction. In embodiments of theinvention, information is transmitted from the transmit coil to thereceive coil using a near-field magnetic induction link. In embodimentsof the invention, the output of the contact hearing device varies byless than two decibels sound pressure level (dB SPL) when the distancebetween the transmit and receive coils varies by between three and sevenmillimeters. In embodiments of the invention, the receive coil is a partof a receive coil assembly, the receive coil assembly including: thereceive coil; at least one disk positioned at a distal end of thereceive coil, the at least one disk including a ferromagnetic material.In embodiments of the invention, the receive coil is wound with acentral core of a non-ferromagnetic material. In embodiments of theinvention, the non-ferromagnetic material is, at least in part, air. Inembodiments of the invention, an outer diameter of the at least one diskis substantially the same as an outer diameter of the receive coil. Inembodiments of the invention, the at least one disk includes a holetherethrough. In embodiments of the invention, the at least one disk istwo disks. In embodiments of the invention, a printed circuit boardincluding electronic components is affixed to a side of the at least onedisk opposite a side to which the receive coil is affixed. Inembodiments of the invention, the electronic components on the printedcircuit board include a demodulation circuit. In embodiments of theinvention, the demodulation circuit is a diode demodulator. Inembodiments of the invention, the at least one disk includes a ferritematerial.

In embodiments of the invention, the transmit coil may include a coilwith an air core. In embodiments of the invention, the transmit coil mayinclude a coil wound around a ferrite core. In embodiments of theinvention, the transmit coil may include a coil wound around a ferritecore with a channel through the center of the ferrite core, the channelforming an opening from the proximal end to the distal end of theferrite core. The channel may further be positioned and sized to form anacoustic vent, allowing sound to pass through the ferrite core. Inembodiments of the invention, the receive coil may include a coil woundaround an air core. In embodiments of the invention, the receive coilmay include a coil wound around ferrite core.

As illustrated in FIGS. 33-35, in embodiments of the invention, thecentral axis of the receive core and the central axis of the transmitcore may be substantially parallel when the ear tip and the contacthearing device are positioned in the ear canal of a user. In embodimentsof the invention, the central axis of the receive core and the centralaxis of the transmit core form an angle of not greater than 15 degrees.In embodiments of the invention, the central axis of the receive coreand the central axis of the transmit core form an angle of not more thanapproximately 25 degrees. In embodiments of the invention, the systemhas a signal reduction of less than 0.5 dB over an angle of between plusand minus 20 degrees from full alignment.

In embodiments of the invention, a reduction in output (in dB) for areceive coil assembly as a function of the transmit to receive coilangle as a function of the distance L, and the angles θ₁, θ₂ and θ₃ overa range of ±45°. In embodiments of the invention, the angle θ may begreater than ±45° and distance between the transmit coil and the receivecoil may be between 2 and 12 mm.

As illustrated in FIGS. 44, 45, 46A and 46B, a receive circuit assembly1084 may include receive circuit board 1074, which may have mountedthereon receive circuit components 1072. Receive circuit assembly mayfurther include receive coil winding (Rx Coil) 1080 and ferrite disk(s)1078. Ferrite disc(s) 1078 may be attached to receive circuit board 1074by adhesive 1076. Receive coil winding 1080 may include a plug 1082 at aproximal end thereof. In embodiments of the invention, receive coilwinding 1080 may be wound around a core of a non-ferromagnetic material,such as, for example air. In embodiments of the invention, ferritedisk(s) 1078 may include a hole in the center of the disks. Inembodiments of the invention, the hole in the center of ferrite disk(s)1078 may be substantially the same diameter as the core of receive coilwinding 1080. FIG. 46A illustrates the flux path through receive circuitassembly 1084 wherein the flux may be generated by an ear tip which islocated a distance away from receive circuit assembly 1084 in the earcanal of a user. In embodiments of the invention, the magnetic flux maybe generated in a coil positioned in the ear tip and may be a signalrepresentative of information (e.g. audio information) to be transmittedto a contact hearing device which includes receive circuit assembly1084. In FIG. 46A flux enters receive circuit assembly 1084 at aproximal end thereof and passes through receive coil winding 1080 andthen through ferrite disk(s) 1078. In FIG. 46A the flux passing throughreceive circuit assembly 1084 induces a current in receive coil winding1080. In embodiments of the invention, the current induced in receivecoil winding 1080 will be conducted electrical components on contacthearing device 112, which will demodulate the received signal andtransmit that signal to a microactuator 140 which may be in contact withthe tympanic membrane of a user.

In embodiments of the invention, receive circuit assembly 1084 includesreceive coil windings 1080 which may be backed by one or more (e.g. two)two ring-shaped ferrite layers (which may also comprise or be referredto as ferrite disk(s)) 1078 to which receive circuit components (e.g.one of the demodulator circuit described herein) are attached. Inembodiments of the invention, the ferrite layers may increase thestrength of the received signals in multiple ways.

In embodiments of the invention, the ferrite layers may increasing theinductance and Q of receive circuit assembly 1084. In embodiments of theinvention, the ferrite layers may shunt magnetic flux entering receivecoil windings 1080 to the outside of receive coil windings 1080 on thedistal (PCB) end of receive coil windings 1080. In embodiments of theinvention, magnetic flux may be shunted because the ferrite layers havehigh permeability and low reluctance compared to air and PCB material.In embodiments of the invention, this shunting of the magnetic fluxresults in the magnetic field being coupled more tightly around thereceive coil windings 1080, which increases inductance withoutsignificant effect on the AC resistance. The Q increases directly fromits defining equation Q=2πfL/R_(AC), where f is the carrier frequencyand L and R_(AC) are the inductance and resistance at the carrierfrequency, respectively.

In embodiments of the invention, shunting the field, the ferrite layersalso shield receive circuit board 1074 and receive circuit components1072 from the magnetic field and reduce loading of the magnetic field byeddy currents in the metal traces of receive circuit board 1075. As aresult, the field inside receive coil windings 1080 is stronger,compared to a receive circuit assembly 1084 which did not include anyferrite layers (e.g. ferrite disk(s) 1078 and, therefore, may produce ahigher signal strength at the output of receive circuit assembly 1084.

In embodiments of the invention, by acting as spacers to separatereceive circuit board 1074 from a distal end of receive coil windings1080 decreases magnetic-field loading caused by the presence of receivecircuit board 1074 and receive circuit components 1072 at the distal endof receive coil windings 1080.

In embodiments of the invention, ferrite disk(s) 1078 may comprise asingle layer of ferrite material. In embodiments of the invention,ferrite disk(s) 1078 may be a ferrite powder embedded in a rubberymatrix. In embodiments of the invention, the ferrite layers, ferritedisks or ferrite rings described herein may be made of any suitableferromagnetic material.

In embodiments of the invention, the present invention is directed to acontact hearing system including: a transmit coil positioned in an eartip wherein the transmit coil includes an electrical coil wound on aferrite core; a receive coil positioned on a contact hearing devicewherein the receive coil includes an electrical coil wound on anon-ferrite core. In embodiments of the invention, the non-ferrite coreincludes air. In embodiments of the invention, the receive coil is acomponent of a receive coil assembly, the receive coil assemblyincluding at least one ferrite disk positioned at a distal end of thereceive coil. In embodiments of the invention, the at least one ferritedisk includes a hole in a center of the at least one ferrite spacer. Inembodiments of the invention, the at least one ferrite disk includes aplurality of ferrite disks laminated together. In embodiments of theinvention, the at least one ferrite disk includes two or more ferritedisks. In embodiments of the invention, the receive coil includes afirst central axis and the at least one ferrite disk includes a secondcentral axis, the first central axis and the second central axis beingaligned. In embodiments of the invention, the ferrite core includes achannel extending from a proximal to a distal end thereof. Inembodiments of the invention, a central axis of the transmit coil and acentral axis of the receive coil are substantially parallel when the eartip and the contact hearing device are positioned in an ear canal of auser. In embodiments of the invention, a central axis of the transmitcoil and a central axis of the receive coil form an angle ofapproximately 15 degrees or less when the ear tip and the contacthearing device are positioned in an ear canal of a user. In embodimentsof the invention, a central axis of the transmit coil and a central axisof the receive coil form an angle of approximately 25 degrees or lesswhen the ear tip and the contact hearing device are positioned in an earcanal of a user. In embodiments of the invention, a distal end of thetransmit coil is positioned within between three and seven millimetersof the proximal end of the receive coil.

In embodiments of the invention, the present invention is directed to acontact hearing system, the contact hearing system including: an eartip, the ear tip including a transmit coil wherein the transmit coil iswound around a core including, at least in part, a ferromagneticmaterial; and a contact hearing device including a receive coil whereinthe receive coil is wound around a core including, at least in part, anon-ferromagnetic material. In embodiments of the invention, theferromagnetic material includes a ferrite material. In embodiments ofthe invention, the non-ferromagnetic material includes air. Inembodiments of the invention, the contact hearing device includes areceive circuit assembly, the receive circuit assembly including: thereceive coil; a disk attached to a distal end of the receive coilwherein the disk includes a ferromagnetic material. In embodiments ofthe invention, the disk has a diameter which is substantially the sameas a diameter of the receive coil. In embodiments of the invention, thedisk has a hole in its center. In embodiments of the invention, thereceive circuit assembly further includes a printed circuit boardincluding electronic components. In embodiments of the invention, thedisk acts as a spacer to separate the printed circuit board from adistal end of the receive coil. In embodiments of the invention,magnetic flux lines entering a proximal end of the receive coil are bentaway from the printed circuit board by the disk as they exit a distalend of the receive coil. In embodiments of the invention, at least aportion of magnetic flux lines entering a proximal end of the receivecoil are prevented from reaching the printed circuit board as they exita distal end of the receive coil. In embodiments of the invention, thepresence of the disk increases a quality factor (Q) of the receivecircuit assembly. In embodiments of the invention, the disk reduces eddycurrents in conductive traces on the printed circuit board when magneticflux is passed through the receive coil. In embodiments of theinvention, the printed circuit board includes components of ademodulation circuit.

In embodiments of the invention, the transmit and/or receive coils maybe encapsulated using a parylene coating.

In embodiments of the invention, the Q (where Q is defined as the ratioof the energy stored in the resonator to the energy supplied by a to it,per cycle, to keep signal amplitude constant, at a frequency where thestored energy is constant with time) of the transmit circuit (“Tx Q”) ishigher than the Q of the contact hearing device (“Rx Q”). In embodimentsof the invention, the Tx Q may be greater than or equal to 70 and the RxQ may be less than or equal to 20. In embodiments of the invention, theRx Q is maximized by moving all circuitry to a board outside of the Rxcoil. In embodiments of the invention, a ferrite core is used toincrease the Q of the transmit coil. In embodiments of the invention,the transmit signal is amplified by exciting the transmit coil to a highstate of resonance. FIG. 52 is an illustration of a system according tothe present invention wherein a transmit circuit according to thepresent invention is tuned to have a higher Q than a receive circuitaccording to present invention. In embodiments of the invention, thetransmit circuit may have a Q of between approximately 50 and 75. Inembodiments of the invention, the transmit circuit may have a Q ofapproximately 60. In embodiments of the invention, the receive circuitmay have a Q of between approximately 15 and 25.

In one embodiment, the present invention is directed to a contacthearing system including: an ear tip including a transmit circuit havinga first Q value, wherein the ear tip includes a transmit coil wound on aferrite core; a contact hearing device including a receive circuithaving a second Q value, wherein the first Q value is greater than thesecond Q value; a receive coil positioned on the contact hearing device,wherein the receive coil includes a core of a non-ferromagneticmaterial. In embodiments of the present invention, the first Q value isgreater than the second Q value by a factor of at least two. Inembodiments of the present invention, the receive coil includes a diskincluding a ferromagnetic material at a distal end thereof. Inembodiments of the present invention, the disk includes a ferritematerial. In embodiments of the present invention, the disk includes ahole in its central portion. In embodiments of the present invention,the transmit coil is inductively coupled to the receive coil. Inembodiments of the present invention, the contact hearing deviceincludes a diode detector connected to the receive coil. In embodimentsof the present invention, the contact hearing device includes a balancedarmature microactuator connected to the receive coil. In embodiments ofthe present invention, the contact hearing device includes a platformwhich supports the receive coil, wherein the platform conforms to theanatomy of the wearers ear canal. In embodiments of the presentinvention, the contact hearing device includes a platform which supportsthe receive coil, wherein the platform is adapted to position thecontact hearing device on a wearer's tympanic membrane.

In one embodiment, the present invention is directed to a method ofinductively coupling an ear tip having a transmit circuit to a contacthearing device having a receive circuit, wherein the transmit circuithas a first Q value and the receive circuit has a second Q value, thefirst Q value being greater than the second Q value, the methodincluding the steps of: exciting a transmit coil in the transmitcircuit, the transmit coil being positioned in an ear tip; radiating anelectromagnetic field from the transmit coil to a receive coil;receiving the radiated electromagnetic field at the receive coil, thereceive coil being positioned on a contact hearing device; andtransmitting information from the transmit coil to the receive coilusing the electromagnetic field. In embodiments of the presentinvention, the first Q value is at least twice as large as the second Qvalue. In embodiments of the present invention, the transmit coilincludes a ferrite core. In embodiments of the present invention, thereceive coil includes a ferrite disk at a distal end thereof. Inembodiments of the present invention, ferrite disk includes a hole inits central portion. In embodiments of the present invention, theinformation is transmitted from the transmit coil to the receive coilusing near field radiation. In embodiments of the present invention, thetransmit coil is inductively coupled to the receive coil. In embodimentsof the present invention, the electromagnetic radiation induces acurrent in the receive coil. In embodiments of the present invention,the current induced in the receive coil is proportional to a level ofmagnetic flux passing through the receive coil. In embodiments of thepresent invention, a current induced in the receive coil drives abalanced armature microactuator positioned on the contact hearingdevice.

In one embodiment, the present invention is directed to a contacthearing system including: an ear tip including a transmit circuit havinga first Q value, wherein the ear tip includes a transmit coil wound on aferrite core, the first Q being in a range of between fifty andseventy-five; a contact hearing device including a receive circuithaving a second Q value, wherein the second Q value is in the range ofbetween fifteen and twenty-five; a receive coil positioned on thecontact hearing device, wherein the receive coil has a core ofnon-ferromagnetic material. In embodiments of the present invention, thereceive coil is a component of a receive circuit assembly, the receivecircuit assembly including a disk at a distal end of the receive coil,wherein the disk includes a ferromagnetic material. In embodiments ofthe present invention, the receive coil assembly further includes aprinted circuit board, the printed circuit board being separated fromthe distal end of the receive coil by the disk.

In a standard systems for transmitting information using electromagneticwaves it would be conventional to design the system such that both thetransmit and receive circuits were optimized around the carrierfrequency, that is that the transmitter would have its highest output atthe carrier frequency and the receive circuit would have its mostefficient reception at the carrier frequency (e.g. the receive coil orantenna would be optimized to pass signals at the carrier frequency withthe least loss). In such a system it would be conventional to tune thetransmitter (Tx) and receiver (Rx) resonance, to maximize powertransfer. For example, you would tune both circuits to have a maximum Qwith the pass band for both the Tx and Rx centered around the carrierfrequency. Resonance generally occurs at (Where L is inductance and C iscapacitance):

$f_{0} = {\frac{\omega_{0}}{2\pi} = {\frac{1}{2\; \pi \sqrt{LC}}.}}$

Where AM modulation is used, such as in inductively coupled systemsaccording to the present invention, that standard tuning may result inIntermodulation Distortion and/or harmonic distortion. IntermodulationDistortion (IMD) may be defined as the ratio (in dB) between the powerof fundamental tones and third-order distortion products which may,under certain circumstances be audible to a listener, for example, ahearing aid user. In a system such as a contact hearing, system IMD maymanifest itself as distortion of words and letters which incorporatehigher frequency tones (e.g. “S” and “T” sounds). This is a particularproblem in such systems because contact hearing systems transmit anddeliver those sounds directly to the tympanic membrane throughmechanical manipulation of the tympanic membrane, unlike conventionalhearing aids.

In embodiments of the present invention, it may be possible to reduce oreliminate such intermodulation distortion by tuning the receive coil tocenter the passband at a frequency above the frequency of the carrier.In embodiments of the invention, the center of the receive passband maybe tuned to approximately 137 KHz above the carrier frequency. Inembodiments of the invention, the center of the bandpass may be tuned toapproximately 322 KHz above the carrier frequency. Thus, by tuning theRx circuit in a manner which would be expected to result in lowerefficiency (power transfer), the present invention reduces or eliminatesintermodulation distortion. In embodiments of the invention, the Rxcircuit is tuned such that the new center of the passband is above thecarrier frequency while the transmit (Tx) circuit is tuned such that thecenter of the passband for the transmit (Tx) circuit is below thetransmit frequency.

FIG. 52 is a graph showing passband tuning according to the presentinvention for a transmit circuit and a receive circuit according to thepresent invention. In FIG. 52 a transmit circuit is tuned such that thecenter of its passband is at the system carrier frequency (e.g. 2.560MHz), while the receive passband is tuned such that the center of itspassband is at a second, higher, frequency (e.g. 2.852). Further, asillustrated in FIG. 52 the transmit circuit is tuned to have a higher Qthan the receive band. In embodiments of the invention, the transmit andreceive circuits are tuned to have an offset between the center of thetransmit passband and the center of the receive passband in order toimprove intermodulation distortion. In embodiments of the invention, thetransmit and receive circuits are tuned to have an offset between thecenter of the transmit passband and the center of the receive passbandin order to improve power transmission from the transmitter to thereceiver. In embodiments of the invention, the transmit and receivecircuits are tuned to have an offset between the center of the transmitpassband and the center of the receive passband in order to increaseoutput power at the contact hearing device. In embodiments of theinvention, the center frequencies of the receive passband may be lowerthan the center frequency of the transmit passband.

In embodiments of the invention, the relationship between the transmitpassband and the receive passband may be such that a signal at afrequency which is at the center of the transmit passband (e.g. acarrier signal) would be attenuated by between approximately 10 dB and15 dB if it were passed through a filter having the characteristics ofthe receive passband. In embodiments of the invention, the relationshipbetween the transmit passband and the receive passband may be such thata signal at a frequency which is at the center of the receive passbandwould be attenuated by between approximately 20 dB and 25 dB if it werepassed through a filter having the characteristics of the receivepassband.

In embodiments of the invention, the present invention is directed to acontact hearing system including: a transmit circuit including atransmit coil positioned in an ear tip, THE transmit circuit having afirst bandpass characteristic, wherein the transmit circuit is tunedsuch that a center of the first bandpass characteristic is set at afirst frequency; and a receive circuit including a receive coilpositioned on a contact hearing device, the receive circuit having asecond bandpass characteristic, wherein the receive circuit is tunedsuch that a center of the second bandpass characteristic differs fromthe center of the first bandpass characteristic. In embodiments of theinvention, the transmit circuit is tuned such that the center of thefirst bandpass characteristic is a transmit carrier frequency. Inembodiments of the invention, the transmit carrier frequency isapproximately 2.56 MHz. In embodiments of the invention, the receivecircuit is tuned such that the center of the second bandpasscharacteristic is tuned to a frequency which is higher than the firstfrequency. In embodiments of the invention, the receive circuit is tunedsuch that the center of the second bandpass characteristic is tuned to afrequency above a transmit carrier frequency. In embodiments of theinvention, the receive circuit is tuned such that the center of thesecond bandpass characteristic is tuned to approximately 2.852 MHz. Inembodiments of the invention, the receive circuit is tuned such that thecenter of the second bandpass characteristic is tuned to a frequencywithin 5 percent of the carrier frequency. In embodiments of theinvention, the receive circuit is tuned such that the center of thesecond bandpass characteristic is tuned to a frequency within 10 percentof the carrier frequency. In embodiments of the invention, the receivecircuit is tuned such that the center of the second bandpasscharacteristic is tuned to a frequency which is within the bandpasscharacteristics of the transmit circuit.

In embodiments of the invention, the present invention is directed to acontact hearing system including: a transmit circuit including atransmit coil positioned in an ear tip, the transmit circuit having afirst passband, wherein the transmit circuit is tuned such that a centerof the first passband is set at a first frequency; and a receive circuitincluding a receive coil positioned on a contact hearing device, thereceive circuit having a second passband, wherein the receive circuit istuned such that a center of the second passband differs from the centerof the first passband.

In embodiments of the invention, the present invention is directed to acontact hearing system including: a transmit circuit including atransmit coil positioned in an ear tip, the transmit circuit having afirst bandpass characteristic, wherein the transmit circuit is tunedsuch that a center of the first bandpass characteristic is set at afirst frequency; a receive circuit including a receive coil positionedon a contact hearing device, the receive circuit having a secondbandpass characteristic, wherein the receive circuit is tuned such thata center of the second bandpass characteristic differs from the centerof the first bandpass characteristic; and wherein the receive circuit istuned such that the center of the second bandpass characteristic istuned to a frequency which is lower than the first frequency. Inembodiments of the invention, the receive circuit is tuned such that thecenter of the second bandpass characteristic is tuned to a frequencybelow a transmit carrier frequency. In embodiments of the invention, thereceive circuit is tuned such that the center of the second bandpasscharacteristic is tuned to a frequency within 5 percent of the carrierfrequency. In embodiments of the invention, the receive circuit is tunedsuch that the center of the second bandpass characteristic is tuned to afrequency within 10 percent of the carrier frequency. In embodiments ofthe invention, the receive circuit is tuned such that the center of thesecond bandpass characteristic is tuned to a frequency which is withinthe bandpass characteristics of the transmit circuit.

In embodiments of the invention, the present invention is directed to amethod of tuning a transmit circuit and a receive circuit, wherein thetransmit and receive circuit form components of a contact hearingsystem, the transmit circuit having a bandpass characteristic and thereceive circuit having a bandpass characteristic, the method includingthe steps of: tuning the bandpass characteristics of the transmitcircuit such that a center of the transmit bandpass characteristic isset to a first frequency; and tuning the bandpass characteristics of thereceive circuit such that a center of the receive bandpasscharacteristic is set to a second frequency, the second frequencydiffering from the first frequency. In embodiments of the invention,second frequency is higher than the first frequency. In embodiments ofthe invention, the first frequency is the transmit carrier frequency. Inembodiments of the invention, the first frequency is approximately 2.56MHz. In embodiments of the invention, the transmit circuit includes atransmit coil wound on a ferrite core, the transmit coil and ferritecore being positioned in an ear tip. In embodiments of the invention,the receive circuit includes a receive coil positioned on a contacthearing device. In embodiments of the invention, the transmit circuitand the receive circuit are adapted to be positioned in the ear canal ofa user. In embodiments of the invention, the first frequency is selectedto be less than 10% lower than the second frequency. In embodiments ofthe invention, the first frequency is selected to be less than 5 percentlower than the first frequency. In embodiments of the invention, thesecond frequency is within the bandpass characteristics of the transmitcircuit. In embodiments of the invention, the second frequency isselected such that, if passed through a filter having the bandpasscharacteristics of the transmit circuit it would be attenuated by lessthan six decibels. In embodiments of the invention, the second frequencyis selected such that, if passed through a filter having the bandpasscharacteristics of the receive circuit it would be attenuated by lessthan three decibels.

In embodiments of the invention, the present invention is directed to amethod of tuning a transmit circuit and a receive circuit, wherein thetransmit and receive circuit form components of a contact hearingsystem, the transmit circuit having a passband and the receive circuithaving a passband, the method including the steps of: tuning thepassband of the transmit circuit such that a center of passband of thetransmit circuit is set to a first frequency; and tuning the bandpasscharacteristics of the receive circuit such that a center of thepassband of the receive circuit is set to a second frequency, the secondfrequency differing from the first frequency.

In embodiments of the invention, the present invention is directed to amethod of tuning a transmit circuit and a receive circuit, wherein thetransmit and receive circuit form components of a contact hearingsystem, the transmit circuit having a bandpass characteristic and thereceive circuit having a bandpass characteristic, the method includingthe steps of: tuning the bandpass characteristics of the transmitcircuit such that the center of the bandpass is set to a firstfrequency; and tuning the bandpass characteristics of the receivecircuit such that the center of the bandpass is set to a secondfrequency, the second frequency differing from the first frequencywherein the second frequency is lower than the first frequency. Inembodiments of the invention, the first frequency is a transmit carrierfrequency. In embodiments of the invention, the transmit circuitincludes a transmit coil wound on a ferrite core, the transmit coil andferrite core being positioned in an ear tip. In embodiments of theinvention, the receive circuit includes a receive coil positioned on acontact hearing device. In embodiments of the invention, the transmitcircuit and the receive circuit are adapted to be positioned in an earcanal of a user. In embodiments of the invention, the first frequency isselected to be less than 10% lower than the second frequency. Inembodiments of the invention, the first frequency is selected to be lessthan 5 percent lower than the first frequency. In embodiments of theinvention, the second frequency is within the bandpass characteristicsof the transmit circuit. In embodiments of the invention, the secondfrequency is selected such that, if passed through a filter having thebandpass characteristics of the transmit circuit it would be attenuatedby less than six decibels. In embodiments of the invention, the secondfrequency is selected such that, if passed through a filter having thebandpass characteristics of the transmit circuit it would be attenuatedby less than three decibels. In embodiments of the invention, the secondfrequency is selected such that, if passed through a filter having thebandpass characteristics of the transmit circuit it would be attenuatedby between 20 and 25 decibels. In embodiments of the invention, thefirst frequency is within the bandpass characteristics of the receivecircuit. In embodiments of the invention, the first frequency isselected such that, if passed through a filter having the bandpasscharacteristics of the receive circuit it would be attenuated by between10 and 15 decibels. In embodiments of the invention: the secondfrequency is selected such that, if passed through a filter having thebandpass characteristics of the transmit circuit it would be attenuatedby between 20 and 25 decibels; and the first frequency is selected suchthat, if passed through a filter having the bandpass characteristics ofthe receive circuit it would be attenuated by between 10 and 15decibels.

In embodiments of the invention, signals may be transmitted between theear tip and the contact hearing device using an amplitude modulatedoscillating magnetic field with a 2.5 MHz carrier frequency. Inembodiments of the invention, the digital audio signal generated by theaudio processor may be mixed with a carrier at the desired couplingfrequency. In embodiments of the invention, the coupling circuitincluding the transmit coil subsystem and the receive coil subsystem mayact as a band pass filter and the resulting waveform is an AM modulatedsignal which may be detected by the diode circuit connected to thereceive coil. In embodiments of the invention, driver circuit may be atype D (H Bridge) and the mixing may be accomplished using an AND or aNAND gate with the carrier and the delta sigma digital modulation signal(the output of the delta sigma modulator, which may be a digital streamrepresentative of an audio signal). In embodiments of the invention, thetwo legs of the H Bridge may be driven 180 degrees out of phase. Inembodiments of the invention, the second leg may be driven by just theinverted (with respect to the other leg) carrier signal, allowingindependent control of an additional carrier signal. This additionalcarrier may be used to overcome distortion caused by the non-linearcurrent-voltage relationship of the diodes near the forward voltageV_(f) without sacrificing the dynamic range of the delta sigmamodulator. The carrier leg voltage source can be independentlycontrolled to adjust the amount of additional carrier inserted. Inembodiments of the invention, the modulation may be FM or FrequencyModulation.

FIGS. 28, 49, and 50 are an illustrations of a circuit that uses a deltasigma modulator (DSM) signal input to modulate a carrier signal in astandard H-Bridge configuration. In embodiments of the invention, eachside is driven 180 degrees out of phase with respect to each other. InFIGS. 28, 49, and 50, the H-Bridge circuit may comprise one or moreAND/NAND circuits 1086, in combination with switches 1088, 1090, 1092and 1094. The output of the H-Bridge may be supplied to transmit coil290 to provide an AM signal field which may transmitted to a receivecoil 130 by, for example, inductively coupling the output of transmitcoil 290 to receive coil 130. In embodiments of the invention,illustrated in FIGS. 49 and 50, one side of the H-Bridge may be coupledto transmit coil 290 through a capacitor C1 Modulation is accomplishedusing the multiplicative property of the AND/NAND function. FIGS. 28,49, and 50 are illustrations of a circuit according to the presentinvention wherein the DSM input is the delta sigma digital modulationsignal. In embodiments of the invention, the output of the delta-sigmamodulator is a signal representative of the sound received by theprocessor which is to be transmitted to the contact hearing device byamplitude modulation (AM) of the carrier. In FIGS. 28, 49, and 50, thecarrier may be a clock signal. In FIGS. 28, 49, and 50, the carrierclock signal may be twice the DSM rate. FIGS. 28, 49 and 50, the carriermay be a digital clock signal representative of the carrier frequency,for example, 2.5 MHz. In embodiments of the invention, switches S1-S4may be solid state/digital switches, such as, FET transistors. Inembodiments of the invention, S1-S4 may form an H Bridge input to aresonant circuit (capacitor C1 and inductor L1). In embodiments of theinvention, the AM output signal may be formed by filtering thedifferential digital signal using a resonator. L1 may be the transmitcoil 290. In the embodiment of the invention illustrated in FIGS. 28 and50, the input to a first side of the H Bridge is the NAND output of theAND/NAND gate circuit which has as its inputs the DSM signal and theCarrier signal. In the embodiment of the invention illustrated in FIG.49, the input to a first side of the H Bridge is the NAND output of theAND/NAND gate circuit which has as its inputs the DSM signal and theCarrier signal while the input to a second side of the H Bridge is theAND output of the AND/NAND gate circuit which has as its inputs the DSMsignal and the Carrier signal. In embodiments of the invention, V1supply voltage controls the amount of modulated signal powertransmitted. In embodiments of the invention, V2 supply controls theadditional carrier power. In embodiments of the invention, the AND/NANDgate(s) serves as the mixer, multiplying the modulation signal and thecarrier, creating an AM modulation of the carrier.

FIGS. 29 and 51 are system models of a system according to the presentinvention, including transmission and receive tank circuits and adetector circuit. In embodiments of the invention, key components (e.g.the AND and NAND function along with the synchronization of the PulseDensity Modulation (PDM) with the clock) may be implemented using aField Programmable Gate Array (FPGA). Further, the low capacitance FPGAoutput driver (for example, an iCE40 Output Driver from LatticeSemiconductor) may be used to create the H-Bridge. In embodiments of theinvention, time skews and clock jitter can be kept at a minimum byre-clocking the outputs after the logic and just prior to the outputdriver. In embodiments of the invention, the circuit illustrated inFIGS. 29 and 51 may include discrete components to model the parasiticelements in the primary component. For example R2, R3 and C2 may be theparasitic resistance and capacitance in L1.

FIG. 30 illustrates the time domain waveform when the added carrierclock is the same size as the delta sigma signal mixed with the carrierclock.

FIG. 31 illustrates the resulting waveform with a 95% delta sigma withthe added clock. Note that this is an AM signal with a modulation indexof less than 50%. The embodiment illustrated in FIG. 31 may result in alower distortion when using a simple diode detector while leaving thefull dynamic range of the delta sigma modulator.

Several alternative methods of generating additional carrier exist. Inembodiments of the invention, the signal could be generated usingconventional analog means (mixer) then sum in additional carrier. Inembodiments of the invention, the signal may be generated by digitallygenerating the desired waveform (including the added carrier) then usinga high speed DAC (Digital to Analog converter. In embodiments of theinvention, the mixing could also be performed by modulating the supplyvoltage to the H Bridge. In embodiments of the invention, this methodcould also be used to make a very simple cost effective AM modulator andby reversing the phase of the added carrier, suppressing the carrierdouble sideband suppressed carrier DSBSC. For standard AM the second legof the H Bridge would be inverted from the first.

In one embodiment, the present invention is directed to a contacthearing system including: an ear tip including a transmit coil, whereinthe transmit coil is connected to an audio processor, including an HBridge circuit; a first input to the H Bridge circuit including an ANDcircuit wherein a first input to the AND circuit includes a carriersignal and a second input to the AND circuit includes an output of adelta sigma modulation circuit, wherein the delta sigma modulationcircuit is a component of the audio processor; and a second input to theH Bridge circuit including an NAND circuit wherein a first input to theNAND circuit includes a carrier signal and a second input to the NANDcircuit includes an output of the delta sigma modulation circuit. Inembodiments of the invention, an output of a first side of the H Bridgecircuit is connected to a first side of the transmit coil and an outputof a second side of the H Bridge circuit is connected to a second sideof the transmit coil. In embodiments of the invention, a capacitor isconnected between at least one output of the H Bridge circuit and thetransmit coil. In embodiments of the invention, the transmit coil isinductively coupled to a receive coil. In embodiments of the invention,the receive coil is positioned on a contact hearing device. Inembodiments of the invention, the contact hearing device includes adiode detector connected to an output of the receive coil.

In one embodiment, the present invention is directed to a method oftransmitting signals between a transmitter and receiver in aninductively coupled contact hearing system, the method including thesteps of: mixing an output of a delta sigma modulation circuit with acarrier signal using an AND gate; providing an output of the AND gate toa first input of an H Bridge circuit; mixing the output of the deltasigma modulation circuit with the carrier signal using an NAND gate;providing an output of the NAND gate to a second input of the H Bridgecircuit; providing an output of a first side of the H Bridge circuit toa first side of a transmit coil; and providing an output of a secondside of the H Bridge circuit to a second side of the transmit coil. Inembodiments of a method according to the present invention the methodfurther including the steps of: receiving a signal generated by thetransmit coil at a receive coil; passing the received signal through adiode detector. In embodiments of a method according to the presentinvention the method further including the step of: passing the outputof the diode detector to a balanced armature transducer. In embodimentsof the invention, the carrier is AM modulated. In embodiments of theinvention, the diode detector demodulates the AM modulated carrier.

In one embodiment, the present invention is directed to a contacthearing system including: an ear tip including a transmit coil, whereinthe transmit coil is connected to an audio processor, including an HBridge circuit, wherein the transmit coil is connected to the output ofthe H Bridge circuit; a first input to the H Bridge circuit including anAND circuit wherein a first input to the AND circuit includes a carriersignal and a second input to the AND circuit includes an output of adelta sigma modulation circuit, wherein the delta sigma modulationcircuit is a component of the audio processor; and a second input to theH Bridge circuit including the carrier signal. In embodiments of theinvention, the second input is an inverted carrier signal. Inembodiments of the invention, the transmit coil is inductively coupledto a receive coil. In embodiments of the invention, the receive coil ispositioned on a contact hearing device. In embodiments of the invention,the contact hearing device includes a diode detector connected to anoutput of the receive coil.

In one embodiment, the present invention is directed to a method oftransmitting signals between a transmitter and receiver in aninductively coupled contact hearing system, the method including thesteps of: mixing the output of a delta sigma modulation circuit with acarrier signal using an AND gate; providing an output of the AND gate toa first input of an H Bridge circuit; providing a carrier signal to asecond input of an H Bridge circuit; providing an output of a first sideof the H Bridge circuit to a first side of a transmit coil; andproviding an output of a second side of the H Bridge circuit to a secondside of a transmit coil. In a method according to the present inventionthe method further including the steps of: receiving a signal generatedby the transmit coil at a receive coil; passing the received signalthrough a diode detector. In a method according to the present inventionthe method further including the steps of: passing an output of thediode detector to a balanced armature transducer. In embodiments of theinvention, the carrier is AM modulated. In embodiments of the invention,the diode detector demodulates the AM modulated carrier signal.

As described earlier, a Villard, 1-diode demodulator, such as, forexample the circuit illustrated in FIG. 36 may be used as a demodulatorcircuit in embodiments of the present invention. In the circuitillustrated in FIG. 36, receive coil 130 has an inductance L-Rx, whichforms a tank resonator when used in combination with resonance capacitor977, having a tuning capacitance C-tune, which may be modified by thecombined capacitances of the remaining circuit components, including ACfilter capacitor 975 (which may be a series capacitor), Schottky diode1062 and load 1006 (which may be, for example, a microactuator). Inembodiments of the invention, resonance capacitor 977 may have acapacitance C-tune which is composed of 3 0201-size capacitors that arechosen to make the tank circuit resonate near or at the carrierfrequency of approximately 2.5 MHz. In embodiments of the invention, thecarrier frequency may be approximately 2.560 MHz. C-tune, in combinationwith the other components and, in particular, the Villard 1-diodedemodulator may be chosen to provide a high output while minimizingintermodulation distortion (IMD).

In the embodiment of the invention, illustrated in FIG. 36, a signalreceived by contact hearing device 112 and, on a negative half cycle ofthe carrier voltage, charge enters motor node 1066 through first diode1062, which may be, for example, a Schottky diode. On the subsequentpositive half-cycle of the carrier, AC filter capacitor 975 and firstdiode 1062 holds this charge on motor node 1066 while displacementcurrent travels through AC filter capacitor 975 into motor node 1066.This sequence results in a voltage doubling at motor node 1066 on eachcarrier cycle. While acting as an efficient demodulator, a Villardcircuit of the kind described may result in large voltage peaks at motornode 1066, which large peaks may result in distortion, such asintermodulation distortion.

In the embodiment of the invention, illustrated in FIGS. 37, 47 and 48 aGreinacher circuit may be used to demodulate a signal received bycontact hearing device 112. In embodiments of the invention, theGreinacher circuit may be a Villard circuit followed by a peak detector,wherein the peak detector may comprise a second diode 1070 (which may insome embodiments of the invention, be a Schottky diode) and a smoothingcapacitor 1068. The extra diode and capacitor act to smooth out thesharp voltage peaks on the Villard output. In a contact hearing deviceaccording to the present invention, smoothing capacitor 1068 may be usedto present a more consistent output to load 1006. In embodiments of theinvention, smoothing capacitor 1068 may form a tank circuit with load1006 wherein the presence of the tank circuit boosts the output ofcontact hearing device at frequencies around 10 kHz. In embodiments ofthe invention, smoothing capacitor 1068 may form a tank circuit withload 1006 wherein the presence of the tank circuit boosts the output ofcontact hearing device at the high end of the range of frequencies ofinterest (e.g. around 10 kHz). In embodiments of the invention,smoothing capacitor 1068 may form a tank circuit with load 1006 whereinthe presence of the tank circuit boosts the output of contact hearingdevice at frequencies around 10 kHz, thereby ensuring that the output ofcontact hearing device 112 is substantially level across the range offrequencies of interest (e.g. from 100 Hz to 10,000 Hz) and does notfall off as the frequency approaches the higher end of the band. Inembodiments of the invention, the circuit illustrated in FIG. 37 may beused to both minimize intermodulation distortion and maintain the outputof contact hearing device 112 up to a frequency of approximately 10,000Hz. In the embodiment of FIG. 47 the Greinacher (2-diode) circuitincludes an output filter. In the embodiment of FIG. 48 the Greinacher(2-diode) circuit includes an LC output filter.

FIGS. 47 and 48 are illustrations of circuits used to implement aGreinacher demodulator with filter according to the present invention.In embodiments of the invention, the filter is intended to prevent(reduce) the carrier RF reaching the load (motor). In embodiments of theinvention, the filter implementation is preferably low-pass, allowingthe audio signals to pass with minimal attenuation up to 10 kHz whilereducing/blocking the RF at 2.56 MHz or any carrier frequency. Inembodiments of the invention, intermodulation distortion (IMD) isimproved (around 5 dB) with two types of low-pass filters in thisposition. In embodiments of the invention, IMD may be improved by theaddition of a filter to the Greinacher demodulator. In embodiments ofthe invention, the presence of the filter may reduce the amount of RFvoltage on diode output node 1067 which reaching motor node 1066, whichwill reduce the reflected RF from the motor from reaching the diodes(especially D2 at diode output node 1067) and mixing with the originalsignal. Mixing of signals in the diode, because of the non-linear I-Vcurve, results in distortion and may be the main contribution to IMD.

In embodiments of the invention, Villard (single diode) demodulationcircuits may be used to increase the efficiency of the contact hearingdevice as they use a single diode which is only turned on for one halfcycle. Unfortunately, Villard demodulation circuits produce largerspikes as they also act as voltage doublers. In demodulation circuits ofthis kind, the number of diodes in the circuit dictates its efficiency(in part) as the power needed to turn on a diode is not usable in signaltransfer and is, therefore, lost. Greinacher (two diode) demodulationcircuits have advantages over Villard demodulation circuits because thesecond diode of the Greinacher circuit in combination with smoothingcapacitor 1068 smooths out the voltage and current spikes of theVillard, thus ensuring a smother demodulated signal and potentiallyreducing distortion. In addition, the Greinacher circuit is beneficialbecause it smooths out the response of the system across the frequencyband of interest (in this case between approximately 100 Hz and 10,000Hz such that the output of the demodulator is substantially the sameacross that range.

In embodiments of the invention, the present invention is directed to acontact hearing system including: a transmit coil positioned in an eartip wherein the transmit coil includes an electrical coil wound on aferrite core; a receive coil positioned on a contact hearing devicewherein the receive coil includes an electrical coil without a core; aload connected to the receive coil; and a demodulation circuit connectedto the receive coil and the load wherein the demodulation circuitincludes a voltage doubler and a peak detector. In embodiments of theinvention, the demodulation circuit is connected to the load at a motornode. In embodiments of the invention, a tuning capacitor is connectedacross the receive coil. In embodiments of the invention, the voltagedoubler includes a series capacitor connected to a first diode. Inembodiments of the invention, the series capacitor is connected betweena first side of the receive coil and a cathode of the first diode. Inembodiments of the invention, the cathode of the first diode isconnected to a second side of the receive coil. In embodiments of theinvention, the peak detector is connected between an output of thevoltage doubler and the load. In embodiments of the invention, the peakdetector includes a second diode and a smoothing capacitor. Inembodiments of the invention, an anode of the second diode is connectedto the voltage doubler. In embodiments of the invention, a cathode ofthe first diode is connected to an anode of the second diode. Inembodiments of the invention, a cathode of the second diode is connectedto a first side of the smoothing capacitor. In embodiments of theinvention, the cathode of the second diode and the first side of thesmoothing capacitor is connected to a first side of the load. Inembodiments of the invention, a second side of the load is connected toa second side of the smoothing capacitor. In embodiments of theinvention, the first diode is a Schottky diode. In embodiments of theinvention, the second diode is a Schottky diode. In embodiments of theinvention, the load is a microactuator. In embodiments of the invention,the load is a balanced armature microactuator.

FIG. 38 is a side view of a transmit coil for use in an ear tipaccording to the present invention. FIG. 39 is a top view of a transmitcoil for use in an ear tip according to the present invention. FIG. 40is a side perspective view of a transmit coil for use in an ear tipaccording to the present invention. In the embodiments of the invention,illustrated in FIGS. 38-40, transmit coil 290 includes coil winding 316which is wrapped around ferrite core 318, which, in the embodiments ofFIGS. 38-40 may be a solid core with no acoustic vent. Transmit coil 290may further include transmit electronics 342.

FIG. 41 is an end view of an ear tip according to the present invention.FIG. 42 is an end view of an ear tip according to the present invention.FIG. 43 is a side view of an ear tip assembly according to the presentinvention. In the embodiments of the invention, illustrated in FIGS.41-43, ear tip 120 includes transmit coil 290 and acoustic vent 338.Transmit coil 290 may include coil winding 316 and ferrite core 316. Inembodiments of the invention, ferrite core 316 may be constructed of aferrite material or of any magnetic material. In embodiments of theinvention, a distal end of ferrite core 316 may extend beyond a distalend of coil winding 316.

In embodiments of the invention described and claimed herein, the textmay refer to a “medial” or a “lateral” end or side of a device orcomponent. In embodiments of the invention described and claimed herein,the text may refer to a “distal” or a “proximal” end or side of a deviceor component. In embodiments of the invention, “medial” and “distal” mayrefer to the side or end of the device or component which is farthestfrom the outside of the user's body (e.g. at the end of the ear canalwhere the tympanic membrane is found. In embodiments of the invention,“lateral” and “proximal” may refer to the side or end of the device orcomponent which is closest to the outside of the user's body (e.g. atthe open end of the ear canal where the pinna is found).

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the present inventiveconcepts. Modification or combinations of the above-describedassemblies, other embodiments, configurations, and methods for carryingout the invention, and variations of aspects of the invention that areobvious to those of skill in the art are intended to be within the scopeof the claims. In addition, where this application has listed the stepsof a method or procedure in a specific order, it may be possible, oreven expedient in certain circumstances, to change the order in whichsome steps are performed, and it is intended that the particular stepsof the method or procedure claim set forth herebelow not be construed asbeing order-specific unless such order specificity is expressly statedin the claim.

Definitions

Audio Processor—A system for receiving and processing audio signals. Inembodiments of the invention, audio processors may include one or moremicrophones adapted to receive audio which reaches the user's ear. Inembodiments of the invention, the audio processor may include one ormore components for processing the received sound. In embodiments of theinvention, the audio processor may include digital signal processingelectronics and software which are adapted to process the receivedsound. In embodiments of the invention, processing of the received soundmay include amplification of the received sound. In embodiments of theinvention, the output of the audio processor may be a signal suitablefor driving an inductive coil located in an ear tip. Audio processorsmay also be referred to as behind the ear units or BTEs.

Contact Hearing System—A system including a contact hearing device, anear tip and an audio processor. In embodiments of the invention, contacthearing systems may also include an external communication device. Inembodiments of the invention, power and/or data may be transmittedbetween an ear tip and a contact hearing device using inductivecoupling.

Contact Hearing Device—A tiny actuator connected to a customizedring-shaped support platform that floats on the ear canal around theeardrum, where the actuator directly vibrates the eardrum causing energyto be transmitted through the middle and inner ears to stimulate thebrain and produce the perception of sound. In embodiments of theinvention, the contact hearing device may comprise a coil, amicroactuator connected to the coil and a support structure supportingthe coil and microactuator. The contact hearing device may also bereferred to as a Tympanic Contact Actuator (TCA), a Tympanic Lens or aTympanic Membrane Transducer (TMT).

Ear Tip—A structure designed to be placed into and reside in the earcanal of a user, where the structure is adapted to receive signals froman audio processor and transmit signals to the user's tympanic membraneor to a device positioned on or near the user's tympanic membrane (suchas, for example, a contact hearing device). In embodiments of theinvention, the signal may be transmitted using inductive coupling,using, for example, a coil connected to the Ear Tip.

Inductively Driven Hearing Aid System—a contact hearing system whereinsignals are transmitted from an ear tip to a contact hearing deviceusing inductive coupling. In an inductively driven hearing system,magnetic waves may be used to transmit information, power or bothinformation and power from the ear tip to the contact hearing device.

Mag Tip—an ear tip adapted for use in an inductively driven hearing aidsystem. In embodiments of the invention, the mag tip may include aninductive transmit coil.

REFERENCE NUMBERS

Number Element 110 Contact Hearing System 112 Contact Hearing Device 114Grasping Tab 116 Demodulator 118 Sulcus Platform 120 Ear Tip/Mag Tip 122Adhesive 124 Drive Post 126 Oil Layer 128 Charging Status LEDs 130Receive coil 132 Audio Processor 134 AC Adapter Port 136 ChargingStation 138 Charging Slots 140 Microactuator 141 Support Structure 142Electromagnetic waves 144 Springs 220 Umbo Lens 250 Taper Tube 260 Cable290 Transmit Coil 310 External Microphone 312 Transmit Electronics 314Volume/Control Switch 316 Coil Winding 318 Ferrite Core 312 CanalMicrophone 320 Analog to Digital Converter 324 External Communicationand Control Device 330 Digital Signal Processor 332 Central Chamber 334Mounting Recess 336 Secondary Acoustic Vent 338 Acoustic Vent 340Acoustic Input (Audible Sound) 342 Transmit Electronics 700 UpstreamSignal 702 Upstream Data 710 Downstream Signal 712 Downstream Data 720Interface 730 Clock Recovery Circuit 740 Data Recovery Circuit 750Energy Harvesting Circuit 760 Power management Circuit 770 VoltageRegulator 780 Driver 790 Data Processor Encoder 800 Data/SensorInterface 802 External Antenna 804 Bluetooth Circuit 806 Battery 808Power Conversion Circuit 810 Microphones 812 Charging Antenna 814Wireless Charging Circuit 816 Interface Circuit 818 Power/Data Link 822Interface Circuit 823 Biological Sensors 824 Energy Harvesting and DataRecovery Circuit 826 Energy Storage Circuitry 828 Power ManagementCircuitry 831 Matching Network 832 Data/Signal Processing Circuitry 834Microcontroler 836 Driver 838 Microactuator 840 Digital SignalProcessors (shown as MA in FIG. 7 appears to be wrong) 842 Cloud BasedComputer 844 Cell Phone 846 Data Acquisition Circuit 848 MPPT ControlCircuit 852 Current Sensor 854 Capacitor 863 Voltage Meter 865 Rectifierand Converter Circuit 869 Storage Device 872 Parasitic Capacitance 882Load 972 Capacitor 974 Diode 975 AC Filter Capacitor 976 Input Circuit977 Resonance Capacitor (Tuning Capacitor) 978 Output Circuit 980 DriveCoil L1 982 Load Coil L4 984 Resonant Transmit Coil L2 986 ResonantReceive Coil L3 988 Drive (Transmit) Circuit 990 Load (Receive) Circuit992 Transmit Resonant Circuit 994 Receive Resonant Circuit 996 SignalSource 998 Resonant Transmit Capacitor C1 1000 Resonant ReceiveCapacitor C2 1002 Voltage Detector 1004 Rectifier Circuit 1006 Load 1008Receive Inductor Lrx 1010 Receive Capacitor Cr1 1012 Receive CapacitorCr2 1014 Receive Capacitor Cr3 1016 Receive Capacitor Cr4 1018 Diode D1(Schottky) 1020 Diode D2 1022 Diode D3 1024 Diode D4 1026 SmoothingCapacitor 1026 1028 Motor 1030 Motor Resistor (Resistance) 1032 MotorInductor (Inductance) 1034 Diode Bridge 1036 Transmitter 1038 CurrentSource 1040 Output Capacitor C0 1042 Output Coil L1 1044 Voltage Source1046 Capacitive Transformer/Divider 1048 Resistor R1 1050 Capacitor C011052 Capacitor C02 1054 Inductor L1 1056 Parallel Drive Circuit 1058Capacitor C7 1060 Capacitor C1 1062 First Diode 1066 Motor Node 1067Diode Output Node 1068 Smoothing Capacitor 1070 Second Diode 1072Receive Circuit Components 1074 Receive Circuit Board 1076 Adhesive 1078Ferrite Disk(s) 1080 Receive Coil Windings 1082 Adhesive Plug 1084Receive Circuit Assembly 1086 AND/NAND Gate 1088 Switch S1 1090 SwitchS2 1092 Switch S3 1094 Switch S4

1. A contact hearing system comprising: a transmit circuit comprising atransmit coil positioned in an ear tip, THE transmit circuit having afirst bandpass characteristic, wherein the transmit circuit is tunedsuch that a center of the first bandpass characteristic is set at afirst frequency; and a receive circuit comprising a receive coilpositioned on a contact hearing device, the receive circuit having asecond bandpass characteristic, wherein the receive circuit is tunedsuch that a center of the second bandpass characteristic differs fromthe center of the first bandpass characteristic.
 2. A contact hearingsystem according to claim 1, wherein the transmit circuit is tuned suchthat the center of the first bandpass characteristic is a transmitcarrier frequency.
 3. A contact hearing system according to claim 2,wherein the transmit carrier frequency is approximately 2.56 MHz.
 4. Acontact hearing system according to claim 1, wherein the receive circuitis tuned such that the center of the second bandpass characteristic istuned to a frequency which is higher than the first frequency.
 5. Acontact hearing system according to claim 1, wherein the receive circuitis tuned such that the center of the second bandpass characteristic istuned to a frequency above a transmit carrier frequency.
 6. A contacthearing system according to claim 1, wherein the receive circuit istuned such that the center of the second bandpass characteristic istuned to approximately 2.852 MHz.
 7. A contact hearing system accordingto claim 1, wherein the receive circuit is tuned such that the center ofthe second bandpass characteristic is tuned to a frequency within 5percent of the carrier frequency.
 8. A contact hearing system accordingto claim 1, wherein the receive circuit is tuned such that the center ofthe second bandpass characteristic is tuned to a frequency within 10percent of the carrier frequency.
 9. A contact hearing system accordingto claim 1, wherein the receive circuit is tuned such that the center ofthe second bandpass characteristic is tuned to a frequency which iswithin the bandpass characteristics of the transmit circuit.
 10. Amethod of tuning a transmit circuit and a receive circuit, wherein thetransmit and receive circuit form components of a contact hearingsystem, the transmit circuit having a bandpass characteristic and thereceive circuit having a bandpass characteristic, the method comprisingthe steps of: tuning the bandpass characteristics of the transmitcircuit such that a center of the transmit bandpass characteristic isset to a first frequency; and tuning the bandpass characteristics of thereceive circuit such that a center of the receive bandpasscharacteristic is set to a second frequency, the second frequencydiffering from the first frequency.
 11. A method of tuning according toclaim 10, wherein the second frequency is higher than the firstfrequency.
 12. A method of tuning according to claim 10, wherein thefirst frequency is the transmit carrier frequency.
 13. A method oftuning according to claim 12, wherein the first frequency isapproximately 2.56 MHz.
 14. A method of tuning according to claim 10,wherein the transmit circuit comprises a transmit coil wound on aferrite core, the transmit coil and ferrite core being positioned in anear tip.
 15. A method of tuning according to claim 14, wherein thereceive circuit comprises a receive coil positioned on a contact hearingdevice.
 16. A method of tuning according to claim 14, wherein thetransmit circuit and the receive circuit are adapted to be positioned inthe ear canal of a user.
 17. A method according to claim 10, wherein thefirst frequency is selected to be less than 10% lower than the secondfrequency.
 18. A method according to claim 17, wherein the firstfrequency is selected to be less than 5 percent lower than the firstfrequency.
 19. A method according to claim 10, wherein the secondfrequency is within the bandpass characteristics of the transmitcircuit.
 20. A method according to claim 19, wherein the secondfrequency is selected such that, if passed through a filter having thebandpass characteristics of the transmit circuit it would be attenuatedby less than six decibels.
 21. A method according to claim 20, whereinthe second frequency is selected such that, if passed through a filterhaving the bandpass characteristics of the receive circuit it would beattenuated by less than three decibels.
 22. A contact hearing systemcomprising: a transmit circuit comprising a transmit coil positioned inan ear tip, the transmit circuit having a first passband, wherein thetransmit circuit is tuned such that a center of the first passband isset at a first frequency; and a receive circuit comprising a receivecoil positioned on a contact hearing device, the receive circuit havinga second passband, wherein the receive circuit is tuned such that acenter of the second passband differs from the center of the firstpassband.
 23. A method of tuning a transmit circuit and a receivecircuit, wherein the transmit and receive circuit form components of acontact hearing system, the transmit circuit having a passband and thereceive circuit having a passband, the method comprising the steps of:tuning the passband of the transmit circuit such that a center ofpassband of the transmit circuit is set to a first frequency; and tuningthe bandpass characteristics of the receive circuit such that a centerof the passband of the receive circuit is set to a second frequency, thesecond frequency differing from the first frequency.
 24. A contacthearing system comprising: a transmit circuit comprising a transmit coilpositioned in an ear tip, the transmit circuit having a first bandpasscharacteristic, wherein the transmit circuit is tuned such that a centerof the first bandpass characteristic is set at a first frequency; areceive circuit comprising a receive coil positioned on a contacthearing device, the receive circuit having a second bandpasscharacteristic, wherein the receive circuit is tuned such that a centerof the second bandpass characteristic differs from the center of thefirst bandpass characteristic; and wherein the receive circuit is tunedsuch that the center of the second bandpass characteristic is tuned to afrequency which is lower than the first frequency.
 25. A contact hearingsystem according to claim 24, wherein the receive circuit is tuned suchthat the center of the second bandpass characteristic is tuned to afrequency below a transmit carrier frequency.
 26. A contact hearingsystem according to claim 24, wherein the receive circuit is tuned suchthat the center of the second bandpass characteristic is tuned to afrequency within 5 percent of the carrier frequency.
 27. A contacthearing system according to claim 24, wherein the receive circuit istuned such that the center of the second bandpass characteristic istuned to a frequency within 10 percent of the carrier frequency.
 28. Acontact hearing system according to claim 24, wherein the receivecircuit is tuned such that the center of the second bandpasscharacteristic is tuned to a frequency which is within the bandpasscharacteristics of the transmit circuit.
 29. A method of tuning atransmit circuit and a receive circuit, wherein the transmit and receivecircuit form components of a contact hearing system, the transmitcircuit having a bandpass characteristic and the receive circuit havinga bandpass characteristic, the method comprising the steps of: tuningthe bandpass characteristics of the transmit circuit such that thecenter of the bandpass is set to a first frequency; and tuning thebandpass characteristics of the receive circuit such that the center ofthe bandpass is set to a second frequency, the second frequencydiffering from the first frequency wherein the second frequency is lowerthan the first frequency.
 30. A method of tuning according to claim 29,wherein the first frequency is a transmit carrier frequency.
 31. Amethod of tuning according to claim 29, wherein the transmit circuitcomprises a transmit coil wound on a ferrite core, the transmit coil andferrite core being positioned in an ear tip.
 32. A method of tuningaccording to claim 31, wherein the receive circuit comprises a receivecoil positioned on a contact hearing device.
 33. A method of tuningaccording to claim 31, wherein the transmit circuit and the receivecircuit are adapted to be positioned in an ear canal of a user.
 34. Amethod according to claim 29, wherein the first frequency is selected tobe less than 10% lower than the second frequency.
 35. A method accordingto claim 34, wherein the first frequency is selected to be less than 5percent lower than the first frequency.
 36. A method according to claim29, wherein the second frequency is within the bandpass characteristicsof the transmit circuit.
 37. A method according to claim 36, wherein thesecond frequency is selected such that, if passed through a filterhaving the bandpass characteristics of the transmit circuit it would beattenuated by less than six decibels.
 38. A method according to claim37, wherein the second frequency is selected such that, if passedthrough a filter having the bandpass characteristics of the transmitcircuit it would be attenuated by less than three decibels.
 39. A methodaccording to claim 36, wherein the second frequency is selected suchthat, if passed through a filter having the bandpass characteristics ofthe transmit circuit it would be attenuated by between 20 and 25decibels.
 40. A method according to claim 29, wherein the firstfrequency is within the bandpass characteristics of the receive circuit.41. A method according to claim 40, wherein the first frequency isselected such that, if passed through a filter having the bandpasscharacteristics of the receive circuit it would be attenuated by between10 and 15 decibels.
 42. A method according to claim 29, wherein: thesecond frequency is selected such that, if passed through a filterhaving the bandpass characteristics of the transmit circuit it would beattenuated by between 20 and 25 decibels; and the first frequency isselected such that, if passed through a filter having the bandpasscharacteristics of the receive circuit it would be attenuated by between10 and 15 decibels.